Re: [Gambas-user] static const?
Charlie Reinl ha scritto: Am Donnerstag, den 15.04.2010, 21:07 +0300 schrieb Jussi Lahtinen: Yes, you can test it. This should generate error: If 1 = 2 And 1 / 0 Then Print test This should not.: If 1 = 2 And If 1 / 0 Then Print test if itabstrip1.count and tabstrip1[i].caption= can fail, if I understand well. Perhaps I must check a few lines of code... yes you are right for that example (my teacher said never try to divide something by 0). And I do not understand why/what/where that condition is/could be good for ... 1/0 !? but If 1 = 1 And 1 2 Then Print test and If 1 = 1 And If 1 2 Then Print test works the same way. The problem is this. Suppose you have to test a property of a object; if the object exists, and its property value is 1 you do something: if theobjectNULL and theobject.number=1 THEN ... The above statement is wrong, because gambas evaluates the second expression even if the first is false; doing so, it tries to read a property of a non-existent object. I checked the documentation (perhaps a little old), and this behavior is not specified. It is true that you find an alternative syntax, looking strange at first but nice, like IF expr and IF otherexpr THEN ..., but this does say nothing about the classic syntax. Coming from years of programming in C and pascal, I gave for normal that short-circuit is common practice, but this is not the case. So I must check a few lines of code. Better explanation can be found on wikipedia: http://en.wikipedia.org/wiki/Short-circuit_evaluation Ciao, Doriano -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
(my teacher said never try to divide something by 0). And I do not understand why/what/where that condition is/could be good for ... 1/0 !? Dividing by zero is guaranteed error. That is exactly reason why I used it to test if Gambas has short-circuits or not. This is for test purpose only, not for real useful code. but If 1 = 1 And 1 2 Then Print test and If 1 = 1 And If 1 2 Then Print test This doesn't test for short-circuits, because both of them will print test. No indication. My code; If 1 = 2 And If 1 / 0 Then Print test does not create error IF language is short-circuit capable, because execute of statement will stop at 1 = 2. Jussi -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Fabián Flores Vadell ha scritto: 2010/4/14 Doriano Blengino doriano.bleng...@fastwebnet.it: First example. I store some bookmarks... ... I could break out the loop using a logic variable, but this way I save a variable. Or I could test the variable in the loop construct, like this: I don't agree the criteria for saving one variable or one expresion if it is not justified. Well, perhaps my daily work with little CPUs (some have 32 bytes of ram!) drives me to professional bias, but why use a variable if can be avoided? There is more than one reason for this (reported without an order). One: variables have to be declared at the beginning of a block; when I write code, if I want to use a variable I must go back to the start of the code and add the declaration, leaving the old road of my mind. Then I must go back to the relevant part and concentrate again on the code. Two: saving a state to later break a loop is less straightforward than doing it in place. If the logic of an algorithm is concentrated in a single point, instead of being spread around, it is easier to revise - at least for me. Three: I think that fast algorithms are always better than slow ones. It is the duty of a good programmer to write good code: and good code is fast and easy to read. Perhaps, if I was a teacher, I would say different things. But teachers sometimes are a little distant from the reality; and scholars will face it later - when they will be programmers. Speed *is* important, the battle on computer hardware and software is all around performances. That said, using a variable is a cost (even more for interpreted languages like gambas). Well - we must understand each other. By no mean I want to say that using variables is awful - is a technique with pros and cons. Now, image an hypothetical case in that you have to do several conditional actions inside the loop. If you resolves it in that way, the code become hard to understand. Catch the joke: FOR tries = 1 TO 2' to search again from the top DO IF Upper(Left(ME.item.Text, i)) = searchstring THEN ' found item RETURN ENDIF IF ME.MoveBelow() THEN BREAK IF (YOU DONT LIKE) THEN RETURN IF (YOU WANT) THEN RETURN IF (NOT ME ..). THEN BREAK IF (YOU DONT...) THEN BREAK IF (YOU WRITE IN C) THEN RETURN ... LOOP ME.MoveFirst NEXT Ok, I know you wouldn't write something like that. Just I want to serve to show what I mean. Ah ah ah! You are wrong... this is my preferred style. I actually *write* things like that, especially when conditions are related. I mean - suppose you want to test the caption of a tabstrip (oh! what a coincidence...). You must read Tabstrip[i].Caption, but first you have to make sure that Tabstrip[i] really exists. So the test becomes: if (iTabStrip.count) and (tabstrip[i].caption blahblahblah) THEN blahblahblah This is a logical mislead, because it puts together two unrelated concepts: the test on the relevant thing (we look for caption), and a good precaution which has little to do with the algorithm. In fact, I would rewrite it as if itabstrip.count then if tabstrip[i].caption... There is no difference in the final (machine) code, but the second statement looks to me more explanatory. And, to be sincere, there is more. The ambiguity of the first statement is well stressed in other languages (sorry, they exist), where sometimes there is no warranty about the order of evaluation of expressions. For whatever reason, a compiler could evaluate tabstrip[i].caption *before* tabstrip.count. And, of course, the compiler is right - the AND operation is commutative (the two terms can be swapped), like addition and multiplication. Back to gambas - I don't know if the documentation says anything about short-circuit and things like that. May be we can assume it as a standard, that modern languages always do short-circuit, but the concept remains. This is why in many cases I could write, especially in a cycle: if i=tabstrip.count then break if tabstrip[i].caption ... then ... Here, the focus about the counter i, and the usage of .caption is even more separated - two statements instead of one - because they are at two different levels. This is only an example I stretched beyond the reality, but you got it. If you have to do tests (like unit tests) and you have routines with multiple exit points, maybe you will have some coverage problems. What do you think? I think that it is exactly the same thing. If you use a variable to break a loop, or return from a function, then that variable is an exit point. With an additional problem - that the variable can be changed later... a RETURN is always a RETURN instead. At this point, I would add that single return points are, for me, worse than multiple exit point. Excuse me again if I pull in other languages, but now they are
Re: [Gambas-user] static const?
Back to gambas - I don't know if the documentation says anything about short-circuit and things like that. May be we can assume it as a standard, that modern languages always do short-circuit, but the concept remains. Gambas doesn't have short-circuits, you have to write like this: IF a=1 AND IF b=2 THEN Jussi -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Jussi Lahtinen ha scritto: Back to gambas - I don't know if the documentation says anything about short-circuit and things like that. May be we can assume it as a standard, that modern languages always do short-circuit, but the concept remains. Gambas doesn't have short-circuits, you have to write like this: IF a=1 AND IF b=2 THEN Ah! Thanks. So, a statement like this: if itabstrip1.count and tabstrip1[i].caption= can fail, if I understand well. Perhaps I must check a few lines of code... Regards, Doriano -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Am Donnerstag, den 15.04.2010, 19:28 +0200 schrieb Doriano Blengino: Jussi Lahtinen ha scritto: Back to gambas - I don't know if the documentation says anything about short-circuit and things like that. May be we can assume it as a standard, that modern languages always do short-circuit, but the concept remains. Gambas doesn't have short-circuits, you have to write like this: IF a=1 AND IF b=2 THEN Ah! Thanks. So, a statement like this: if itabstrip1.count and tabstrip1[i].caption= can fail, if I understand well. Perhaps I must check a few lines of code... Regards, Doriano Salut, I'v never done it like that (IF a=1 AND IF b=2 THEN), are you sure ? -- Amicalement Charlie -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Yes, you can test it. This should generate error: If 1 = 2 And 1 / 0 Then Print test This should not.: If 1 = 2 And If 1 / 0 Then Print test Jussi On Thu, Apr 15, 2010 at 20:56, Charlie Reinl karl.re...@fen-net.de wrote: Am Donnerstag, den 15.04.2010, 19:28 +0200 schrieb Doriano Blengino: Jussi Lahtinen ha scritto: Back to gambas - I don't know if the documentation says anything about short-circuit and things like that. May be we can assume it as a standard, that modern languages always do short-circuit, but the concept remains. Gambas doesn't have short-circuits, you have to write like this: IF a=1 AND IF b=2 THEN Ah! Thanks. So, a statement like this: if itabstrip1.count and tabstrip1[i].caption= can fail, if I understand well. Perhaps I must check a few lines of code... Regards, Doriano Salut, I'v never done it like that (IF a=1 AND IF b=2 THEN), are you sure ? -- Amicalement Charlie -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Charlie Reinl wrote:
Am Donnerstag, den 15.04.2010, 19:28 +0200 schrieb Doriano Blengino:
Jussi Lahtinen ha scritto:
Back to gambas - I don't know if the documentation says anything about
short-circuit and things like that. May be we can assume it as a
standard, that modern languages always do short-circuit, but the concept
remains.
Gambas doesn't have short-circuits, you have to write like this:
IF a=1 AND IF b=2 THEN
Ah! Thanks. So, a statement like this:
if itabstrip1.count and tabstrip1[i].caption=
can fail, if I understand well. Perhaps I must check a few lines of code...
Regards,
Doriano
Salut,
I'v never done it like that (IF a=1 AND IF b=2 THEN), are you sure ?
Yes, It is clearly there in the manual.
*IF* _Expression_ [ { *AND IF* | *OR IF* } _Expression_ ... ] [ *THEN* ]
...
[ *ELSE IF* _Expression_ [ { *AND IF* | *OR IF* } _Expression_ ... ] [ *THEN* ]
... ]
[ *ELSE*
... ]
*ENDIF*
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Re: [Gambas-user] static const?
I don't agree the criteria for saving one variable or one expresion if it is not justified. Well, perhaps my daily work with little CPUs (some have 32 bytes of ram!) drives me to professional bias, but why use a variable if can be avoided? There is more than one reason for this (reported without an order). One: variables have to be declared at the beginning of a block; when I write code, if I want to use a variable I must go back to the start of the code and add the declaration, leaving the old road of my mind. Then I must go back to the relevant part and concentrate again on the code. I don't see the problem here. When you think about create a variable (or any other memory structure), you never let to think about your algorithm. In fact, if the language require previous variable declaration is a good thing because forces to think about on resources you will use and how you will do that. I think that the choices about memory structures is one of the critical parts when you write an algorithm. So, when you think about variables far away of divert attention, actually you are deepening your understanding about the problem and your algorithmic solution. Two: saving a state to later break a loop is less straightforward than doing it in place. If the logic of an algorithm is concentrated in a single point, instead of being spread around, it is easier to revise - at least for me. Three: I think that fast algorithms are always better than slow ones. I think that if the speed is a requeriment, that's right. But if not, just is right if is to easy to do. So, not always a faster algorithm is better. Let me quote to Donald Knuth when he said premature optimization is the root of all evil (or at least most of it) in programming. It is the duty of a good programmer to write good code: and good code is fast and easy to read. I believe that a good code is one that is simple, and to achieve this goal at least must (sure I forget something): - Uses the correct structures of memory and control - Have high cohesion and low coupling - Be correctly modularized - Uses good names - Be written in order that it is easy to understand it Perhaps, if I was a teacher, I would say different things. But teachers sometimes are a little distant from the reality; and scholars will face it later - when they will be programmers. The industry insists in that the most important things are compliance of requirements and easy maintenance. That said, using a variable is a cost (even more for interpreted languages like gambas). Well - we must understand each other. By no mean I want to say that using variables is awful - is a technique with pros and cons. Easy, I understand you. if (iTabStrip.count) and (tabstrip[i].caption blahblahblah) THEN blahblahblah This is a logical mislead, because it puts together two unrelated concepts: the test on the relevant thing (we look for caption), and a good precaution which has little to do with the algorithm. In fact, I would rewrite it as if itabstrip.count then if tabstrip[i].caption... There is no difference in the final (machine) code, but the second statement looks to me more explanatory. I agree. And, to be sincere, there is more. The ambiguity of the first statement is well stressed in other languages (sorry, they exist), where sometimes there is no warranty about the order of evaluation of expressions. For whatever reason, a compiler could evaluate tabstrip[i].caption *before* tabstrip.count. And, of course, the compiler is right - the AND operation is commutative (the two terms can be swapped), like addition and multiplication. Back to gambas - I don't know if the documentation says anything about short-circuit and things like that. May be we can assume it as a standard, that modern languages always do short-circuit, but the concept remains. I agree. function movefile(src, dst as string) as boolean result = false if not exists(src) then return if not open_and_read(src) then return close(src) if not open_and_write(dst) then return close(dst) result = true end Now comes personal taste. The second routine, for you, is a joke. Oh, no. The joke was: IF (YouWriteInC) THEN RETURN. Maybe, we not share the same humor sense. For me, it looks simpler, shorter, and faster. The only problem I see are those repeated not and return. They are ugly to see, but very clear in saying if this operation fails, then stop. The code coverage should be simpler to do, but I am not really sure. When I have to write many logical tests, I separates them in a new function. That allow me keep the code short and self explanatory. I do this in a extremist way especially when I want to anybody can understand my code. I know this is even more expensive than using a variable. I don't care, I never seen a penalization over performance for that, and if I have to do some optimization, I would do later. I think that the
Re: [Gambas-user] static const?
Am Donnerstag, den 15.04.2010, 21:07 +0300 schrieb Jussi Lahtinen: Yes, you can test it. This should generate error: If 1 = 2 And 1 / 0 Then Print test This should not.: If 1 = 2 And If 1 / 0 Then Print test Jussi On Thu, Apr 15, 2010 at 20:56, Charlie Reinl karl.re...@fen-net.de wrote: Am Donnerstag, den 15.04.2010, 19:28 +0200 schrieb Doriano Blengino: Jussi Lahtinen ha scritto: Back to gambas - I don't know if the documentation says anything about short-circuit and things like that. May be we can assume it as a standard, that modern languages always do short-circuit, but the concept remains. Gambas doesn't have short-circuits, you have to write like this: IF a=1 AND IF b=2 THEN Ah! Thanks. So, a statement like this: if itabstrip1.count and tabstrip1[i].caption= can fail, if I understand well. Perhaps I must check a few lines of code... Regards, Doriano Salut, I'v never done it like that (IF a=1 AND IF b=2 THEN), are you sure ? -- Amicalement Charlie Salut, yes you are right for that example (my teacher said never try to divide something by 0). And I do not understand why/what/where that condition is/could be good for ... 1/0 !? but If 1 = 1 And 1 2 Then Print test and If 1 = 1 And If 1 2 Then Print test works the same way. -- Amicalement Charlie -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Fabián Flores Vadell ha scritto: 2010/4/13 Jussi Lahtinenjussi.lahti...@gmail.com: Just in case: REPEAT b = TabStrip3.Count ' In fact, this does nothing usefull INC a UNTIL a TabStrip3.Count OR TabStrip3[a].Caption = IdCaption This doesn't make same functionality. I can't resist to add my mis-contribute... Back to the beginning: a CONST declaration is something that uses no memory, so it can not have instances, and hence it can not be STATIC. The C language, in facts, does not even have CONSTs - it goes with #define. So, it would be correct to forbid STATIC when declaring CONSTs. On the other hand, a CONST is always static, because the effective data it describes reside in a memory outside the program - they reside in the compiler memory. About the cycles WHILE, FOR, REPEAT and so on, I think the statements BREAK and CONTINUE are very useful (I would add a third statement: RESTART): they permit a finer control and many times they are clearer than complex tests. . Your example only has two test, against COUNT and the CAPTION. What kind of test would you write if the conditions were 15? Perhaps concatenated (I mean, some test are only meaningful when other conditions are met). Finally, your last lines of code do not work: PRIVATE FUNCTION ScanTab(IdCaption AS String) AS Byte DIM a AS Byte = 0 WHILE (a TabStrip1.Count - 1) AND (TabStrip1[a].Text IdCaption) INC a WEND RETURN IF(TabStrip1[a].Caption = IdCaption, a, -1) END Suppose you have a tabstrip with three tabs, and last, Tabstrip1[2] has the caption we want. In the first cycle, we test Tabstrip1[0]: does not match, and a turns 1 In the secon cycle, we test tabstrip1[1]: does not match and a turns 2 The third cycle does not get executed - a is 2, which is not less than 3-1 (it is equal). Moreover, your algorithm does a double test on caption, which could be avoided. Doing an additional test is not an important thing if the test is quick and the routine is called not too much often. What if the routine is called millions time, or the test is more heavy? About not using RETURN or BREAK inside cycles, we must think at different kind of cycles. The WHILE and alike, where no variables are directly involved in the cycle declaration, never have problems - the semantic of the declaration does not imply anything about variable allocation. In the FOR cycles instead, other languages can do strange things, both on allocation and code optimization, so it is effectively a bad idea to fiddle with the loop control variable; in other languages this is not stressed the same way (basic, for example), but actually is, at least, ugly. It seems to me that you have said that an exception would be the FOR EACH cycle... why? Regards, Doriano -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
The C language, in facts, does not even have CONSTs - it goes with
#define. So, it would be correct to forbid STATIC when declaring CONSTs.
Surely this is not correct. ANSI C uses const, and C++ also uses the
const keyword.
#define (a preprocessor directive) is a relic from old C, and const is
now recommended use instead.
Also, it would be correct to use static with const, the line below would
be correct use.
static const int daysPerMonth[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
Having said that, The original question was not about C, I think Fabian
was simply asking about the scope of constants in classes (in Gambas)
Regards
Les Hardy
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Re: [Gambas-user] static const?
Les Hardy ha scritto:
The C language, in facts, does not even have CONSTs - it goes with
#define. So, it would be correct to forbid STATIC when declaring CONSTs.
Surely this is not correct. ANSI C uses const, and C++ also uses the
const keyword.
#define (a preprocessor directive) is a relic from old C, and const is
now recommended use instead.
Surely, according to http://www.ericgiguere.com/articles/ansi-c-summary.html
The declaration:
enum colours { RED, BLUE, GREEN };
would declare colours as an enumeration tag representing the integer
constants RED, BLUE and GREEN. These enumeration constants are given
integer values starting at 0 and increasing by 1 with each identifier.
An enumeration constant may be used wherever an integer is expected.
The following is equivalent to the above enumerated type:
#define RED 0
#define BLUE 1
#define GREEN 2
Moreover, from http://tigcc.ticalc.org/doc/keywords.html
_const_
*Makes variable value or pointer parameter unmodifiable.*
When |const| is used with a variable, it uses the following syntax:
const/variable-name/ [ =/value/];
In this case, the |const| modifier allows you to assign an initial
value to a variable that cannot later be changed by the program. For
example,
const my_age = 32;
Any assignments to |'my_age'| will result in a compiler error.
However, such declaration is quite different than using
#define my_age 32
In the first case, the compiler allocates a memory for |'my_age'| and
stores the initial value 32 there, but it will not allow any later
assignment to this variable. But, in the second case, all occurences
of |'my_age'| are simply replaced with 32 by the preprocessor
http://tigcc.ticalc.org/doc/cpp.html, and no memory will be
allocated for it.
You perhaps refer to const modifier, which is different from declaring
a constant, like in
public:
WinEDA_VertexCtrl( wxWindow* parent, const wxString title,
wxBoxSizer* BoxSizer, int units, int
internal_unit );
Also, it would be correct to use static with const, the line below would
be correct use.
static const int daysPerMonth[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
In this case - talking about C and not C++:
|static| tells that a function or data element is only known within
the scope of the current compile. In addition, if you use the |static|
keyword with a variable that is local to a function, it allows the
last value of the variable to be preserved between successive calls to
that function.
const says that data is not modifiable, so static would say the same
thing. Note also the ambiguity of the keyword when applied to data
global to a module, and data local to a function - the same keyword does
two very different things.
Having said that, The original question was not about C, I think Fabian
was simply asking about the scope of constants in classes (in Gambas)
Uhm... is it forbidden to cite other languages to better explain a
concept? So why you cited C++?
Anyway, you are right, the original question was about scope. In gambas
scope is governed by PRIVATE and PUBLIC. Full stop.
If you feel that my reply is a little hurting, excuse me; it is because
your reply seemed hurting to me. Prove to me that I am wrong and I will
publicly apologize.
Regards,
Doriano
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Re: [Gambas-user] static const?
2010/4/14 Doriano Blengino doriano.bleng...@fastwebnet.it: Back to the beginning: a CONST declaration is something that uses no memory, so it can not have instances, and hence it can not be STATIC. On the other hand, a CONST is always static, because the effective data it describes reside in a memory outside the program - they reside in the compiler memory. Thanks Doriano. I understand that. My question was caused by the fact that the compiler allows use the keyword STATIC in the declaration of constants, even though the online help and a very basic logical reasoning indicate that use the keyword STATIC is unnecesary in this situation About the cycles WHILE, FOR, REPEAT and so on, I think the statements BREAK and CONTINUE are very useful (I would add a third statement: RESTART): they permit a finer control and many times they are clearer than complex tests. You do not give arguments to support your opinion. Can you give me some examples? I think, that these can be obvious for you, but not for me. Your example only has two test, against COUNT and the CAPTION. What kind of test would you write if the conditions were 15? Perhaps concatenated (I mean, some test are only meaningful when other conditions are met). Assign the results of logical expressions to Boolean variables, it is often the way to manage the complexity of conditionals expressions. And in the loops, to use these variables instead of those logical expressions. But I think that you are knowing well this, and you points to the performance of programs. If so, my answer is that the performance isn't a priority in many types of programs, and the evaluation of logical expressions have a little cost in comparation with other operations (I/O, compression, among many others). Finally, your last lines of code do not work: Yes, it works. PRIVATE FUNCTION ScanTab(IdCaption AS String) AS Byte DIM a AS Byte = 0 WHILE (a TabStrip1.Count - 1) AND (TabStrip1[a].Text IdCaption) INC a WEND RETURN IF(TabStrip1[a].Caption = IdCaption, a, -1) END The third cycle does not get executed - a is 2, which is not less than 3-1 (it is equal). That's irrelevant because the external comprobation (the logical expression in the return sentence) Moreover, your algorithm does a double test on caption, which could be avoided. I think that the second test can't to be avoided. If it isn't put out the loop, you have to put into the loop. The reason for include the test (TabStrip1[a].Text IdCaption) in conditional expression is only stop the loop if there's match before get the last item. I think that this code can to write in many ways, but with no significant variations. How would you do? Doing an additional test is not an important thing if the test is quick and the routine is called not too much often. What if the routine is called millions time, or the test is more heavy? I think that the computational cost of evaluate complex logical expressions, generally is insignificant. But if not, then the first thing to be considerated is the language to use, and I see few alternatives: assembler, C, C++, someone else; the second thing is the many optimizations to do. But, what kind the system would be? One that is not possible to do with Gambas. About not using RETURN or BREAK inside cycles, we must think at different kind of cycles. The WHILE and alike, where no variables are directly involved in the cycle declaration, never have problems - the semantic of the declaration does not imply anything about variable allocation. In the FOR cycles instead, other languages can do strange things, both on allocation and code optimization, so it is effectively a bad idea to fiddle with the loop control variable; in other languages this is not stressed the same way (basic, for example), but actually is, at least, ugly. Yep, but I not was thinking in possible collateral effects, derived from implementation of language. (To those, the corresponding compiler would let in evidence, or would become a logical error isn't very difficult to detect and correct). I was thinking in conceptuals implications. This conceptuals implications derives in to use of the language resources in any ways, instead to use them in the correct situations. It seems to me that you have said that an exception would be the FOR EACH cycle... why? FOR EACH really iterates through all items, so there's only way to stop the loop when it's goal is achieved, is by the BREAK sentence used in a conditonal sentence inside the loop. But it might think that if it is necessary to do this, then the iterative structure FOR EACH is not adequate. And I hope that my very ugly english, does not cause tears. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively,
Re: [Gambas-user] static const?
If you feel hurt I am sorry for that, it was not my intention to hurt
you, and I have no wish to prove you wrong.
I do still stand by my statement.
Regards
Les Hardy
Doriano Blengino wrote:
Les Hardy ha scritto:
The C language, in facts, does not even have CONSTs - it goes with
#define. So, it would be correct to forbid STATIC when declaring CONSTs.
Surely this is not correct. ANSI C uses const, and C++ also uses the
const keyword.
#define (a preprocessor directive) is a relic from old C, and const is
now recommended use instead.
Surely, according to http://www.ericgiguere.com/articles/ansi-c-summary.html
The declaration:
enum colours { RED, BLUE, GREEN };
would declare colours as an enumeration tag representing the integer
constants RED, BLUE and GREEN. These enumeration constants are given
integer values starting at 0 and increasing by 1 with each identifier.
An enumeration constant may be used wherever an integer is expected.
The following is equivalent to the above enumerated type:
#define RED 0
#define BLUE 1
#define GREEN 2
Moreover, from http://tigcc.ticalc.org/doc/keywords.html
_const_
*Makes variable value or pointer parameter unmodifiable.*
When |const| is used with a variable, it uses the following syntax:
const/variable-name/ [ =/value/];
In this case, the |const| modifier allows you to assign an initial
value to a variable that cannot later be changed by the program. For
example,
const my_age = 32;
Any assignments to |'my_age'| will result in a compiler error.
However, such declaration is quite different than using
#define my_age 32
In the first case, the compiler allocates a memory for |'my_age'| and
stores the initial value 32 there, but it will not allow any later
assignment to this variable. But, in the second case, all occurences
of |'my_age'| are simply replaced with 32 by the preprocessor
http://tigcc.ticalc.org/doc/cpp.html, and no memory will be
allocated for it.
You perhaps refer to const modifier, which is different from declaring
a constant, like in
public:
WinEDA_VertexCtrl( wxWindow* parent, const wxString title,
wxBoxSizer* BoxSizer, int units, int
internal_unit );
Also, it would be correct to use static with const, the line below would
be correct use.
static const int daysPerMonth[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
In this case - talking about C and not C++:
|static| tells that a function or data element is only known within
the scope of the current compile. In addition, if you use the |static|
keyword with a variable that is local to a function, it allows the
last value of the variable to be preserved between successive calls to
that function.
const says that data is not modifiable, so static would say the same
thing. Note also the ambiguity of the keyword when applied to data
global to a module, and data local to a function - the same keyword does
two very different things.
Having said that, The original question was not about C, I think Fabian
was simply asking about the scope of constants in classes (in Gambas)
Uhm... is it forbidden to cite other languages to better explain a
concept? So why you cited C++?
Anyway, you are right, the original question was about scope. In gambas
scope is governed by PRIVATE and PUBLIC. Full stop.
If you feel that my reply is a little hurting, excuse me; it is because
your reply seemed hurting to me. Prove to me that I am wrong and I will
publicly apologize.
Regards,
Doriano
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proactively, and fine-tune applications for parallel performance.
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Re: [Gambas-user] static const?
Fabián Flores Vadell ha scritto: 2010/4/14 Doriano Blenginodoriano.bleng...@fastwebnet.it: Back to the beginning: a CONST declaration is something that uses no memory, so it can not have instances, and hence it can not be STATIC. Thanks Doriano. I understand that. My question was caused by the fact that the compiler allows use the keyword STATIC in the declaration of constants, even though the online help and a very basic logical reasoning indicate that use the keyword STATIC is unnecesary in this situation And here we return on your idea about a good compiler - and it is mine idea too. A good compiler should be very precise about things that have sense, and can be done, and things that can not be done, or have no meaning. In this respect, it is a nonsense to let the user write a CONST STATIC. But compilers sometimes must keep compatibility with other, older, compilers. So, in this case, may be that VB(tm) was accepting this, and so does gambas. But I don't know VB(tm). Anyway, this issue is harmless, so I don't see it as a big problem. About the cycles WHILE, FOR, REPEAT and so on, I think the statements BREAK and CONTINUE are very useful (I would add a third statement: RESTART): they permit a finer control and many times they are clearer than complex tests. You do not give arguments to support your opinion. Can you give me some examples? I think, that these can be obvious for you, but not for me. First of all, I must say that I see your point. May be that all the issue is about personal style. But I did a quick research in my sources to let you see some example. I have little code in gambas - I use a lot C, about which I could have many examples but, as stated by someone other, it is forbidden to talk about C... First example. I store some bookmarks in a file by using the Settings class. Every bookmark is stored with a name like Bmark1, Bmark2 and so on, but I don't know how many of them are in the file. I know when there are no more values, instead. So the routine is the following: i = 1 DO st = settings[Bmark i, ] IF st = THEN BREAK men = NEW Menu(mnBooks) AS chgBook men.Caption = st INC i LOOP Now, to understand if there are more bookmarks to read, I must try to read it. If the value is NULL, then the job is finished. Clearly, a FOR-NEXT is no good (or, one can write a for-next from 1 to 1000... misleading...). I could break out the loop using a logic variable, but this way I save a variable. Or I could test the variable in the loop construct, like this: i = 1 DO st = settings[Bmark i, ] if st then men = NEW Menu(mnBooks) AS chgBook men.Caption = st ENDIF INC i while st but, as you see, there are TWO tests instead of one, and there is an added line of code. May be that I am missing something, but the BREAK instruction is really useful here. The second example is a textual search on a treeview. If the user types some text, the selection is moved on the next item beginning with that text. If no more items satisfy the criterium, the search must start again at the top, but only once. So the code (there is a ME.MoveBelow() just before this code, I omitted it for simplicity): i = Len(searchstring) FOR tries = 1 TO 2' to search again from the top DO IF Upper(Left(ME.item.Text, i)) = searchstring THEN ' found item RETURN ENDIF IF ME.MoveBelow() THEN BREAK LOOP ME.MoveFirst NEXT Here, the FOR-NEXT is a quick way to execute some code for no more than two times... Again, I could have used a variable to store the result of the test, but I saved it... And again this is not, perhaps, the best code you can see around - but it works, and it is reasonably fast and short. Your example only has two test, against COUNT and the CAPTION. What kind of test would you write if the conditions were 15? Perhaps concatenated (I mean, some test are only meaningful when other conditions are met). Assign the results of logical expressions to Boolean variables, it is often the way to manage the complexity of conditionals expressions. And in the loops, to use these variables instead of those logical expressions. But I think that you are knowing well this, and you points to the performance of programs. If so, my answer is that the performance isn't a priority in many types of programs, and the evaluation of logical expressions have a little cost in comparation with other operations (I/O, compression, among many others). I agree, and partly not. I think that clearness and beatiful code is to prefer against speed, but only when speed is not an issue. In the text-search example speed *is* an issue. Never tried to open a directory with some 3 files in it, and perform a textual search? KDE solves elegantly... it does textual search *only* if the sort order is by name.
Re: [Gambas-user] static const?
Errata corrige: Finally, your last lines of code do not work: Yes, it works. PRIVATE FUNCTION ScanTab(IdCaption AS String) AS Byte DIM a AS Byte = 0 WHILE (aTabStrip1.Count - 1) AND (TabStrip1[a].Text IdCaption) INC a WEND RETURN IF(TabStrip1[a].Caption = IdCaption, a, -1) END The third cycle does not get executed - a is 2, which is not less than 3-1 (it is equal). That's irrelevant because the external comprobation (the logical expression in the return sentence) May be that I am missing something, but... how can you say that it works if it omits to test the last item? Time later, driving to home and still thinking about this routine, I finally recalled what you wanted to say with comprobation. Yes, you are right - your code works. If I would have payed more attention to the routine, I would have noticed. But, stupidly, I concentrated only on the cycle, noting that it was missing a test on the last item. That last item is managed by the last test before exiting. Still I don't like this routine. What happens if TabStrip1.Count=0 (emtpy tabstrip)? Ok, now I'am home, it's late - so good night to everybody (in Europe, of course). Regards, -- Doriano Blengino Listen twice before you speak. This is why we have two ears, but only one mouth. -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
2010/4/14 Doriano Blengino doriano.bleng...@fastwebnet.it: And here we return on your idea about a good compiler - and it is mine idea too. I don't want judge if the Gambas compiler is good or not, I feel that I don't have the knowledge or experience required for do that. But, I shared with you about the taste for a compiler that to say at programmer: This is right. That's not a good idea. First of all, I must say that I see your point. May be that all the issue is about personal style. Yes, I have to admit that the style surely have influence in the beauty criteria. But I did a quick research in my sources to let you see some example. I have little code in gambas - I use a lot C, about which I could have many examples but, as stated by someone other, it is forbidden to talk about C... Ha! Is forbidden if you want that I can understand you. That is true :) First example. I store some bookmarks in a file by using the Settings class. Every bookmark is stored with a name like Bmark1, Bmark2 and so on, but I don't know how many of them are in the file. I know when there are no more values, instead. So the routine is the following: i = 1 DO st = settings[Bmark i, ] IF st = THEN BREAK men = NEW Menu(mnBooks) AS chgBook men.Caption = st INC i LOOP ... I could break out the loop using a logic variable, but this way I save a variable. Or I could test the variable in the loop construct, like this: ... but, as you see, there are TWO tests instead of one, and there is an added line of code. I don't agree the criteria for saving one variable or one expresion if it is not justified. May be that I am missing something, but the BREAK instruction is really useful here. I don't say that BREAK (and other sentences) haven't utility, but that isn't strictly necessary (perhaps I said unnecesary and this word may be incorrect). The second example is a textual search on a treeview. If the user types some text, the selection is moved on the next item beginning with that text. If no more items satisfy the criterium, the search must start again at the top, but only once. So the code (there is a ME.MoveBelow() just before this code, I omitted it for simplicity): i = Len(searchstring) FOR tries = 1 TO 2 ' to search again from the top DO IF Upper(Left(ME.item.Text, i)) = searchstring THEN ' found item RETURN ENDIF IF ME.MoveBelow() THEN BREAK LOOP ME.MoveFirst NEXT Here, the FOR-NEXT is a quick way to execute some code for no more than two times... Again, I could have used a variable to store the result of the test, but I saved it... I think that you use a structure FOR-NEXT that requires to you knowing the amount of iterations to do. But, in this case you know that is likely the number of iterations declared could be unnecesary. So, conceptually, the correct loop would be one that allow control the number of iterations. There isn't a practical problem here. Just a conceptual consideration. This doesn't matter if you understand what you do, like in you case. But I think that's important for who is learning to programming. (I'm sorry, I'm a teacher -and may be some day I have to teach programming-). However, I don't want keep with older patterns of thought. So, will I keep open my mind. Now, image an hypothetical case in that you have to do several conditional actions inside the loop. If you resolves it in that way, the code become hard to understand. Catch the joke: FOR tries = 1 TO 2' to search again from the top DO IF Upper(Left(ME.item.Text, i)) = searchstring THEN ' found item RETURN ENDIF IF ME.MoveBelow() THEN BREAK IF (YOU DONT LIKE) THEN RETURN IF (YOU WANT) THEN RETURN IF (NOT ME ..). THEN BREAK IF (YOU DONT...) THEN BREAK IF (YOU WRITE IN C) THEN RETURN ... LOOP ME.MoveFirst NEXT Ok, I know you wouldn't write something like that. Just I want to serve to show what I mean. I think that clearness and beatiful code is to prefer against speed, but only when speed is not an issue. I agree. In the text-search example speed *is* an issue. Never tried to open a directory with some 3 files in it, and perform a textual search? Ok, I agree. I would do so: PRIVATE FUNCTION ScanTab(IdCaption AS String) AS Byte DIM a AS Byte = 0 WHILE a TabStrip1.Count if TabStrip1[a].Text = IdCaption then return a INC a WEND return -1 END PRIVATE FUNCTION ScanTab(IdCaption AS String) AS Byte DIM a AS Byte for a = 0 to TabStrip1.Count-1 if TabStrip1[a].Text = IdCaption then return a next return -1 END If you have to do tests (like unit tests) and you have routines with multiple exit points, maybe you will have some coverage problems. What do you think? No, the issue is different. Giving any language and any cpu, every operation has a cost. Comparing two
Re: [Gambas-user] static const?
2010/4/14 Doriano Blengino doriano.bleng...@fastwebnet.it: Errata corrige: May be that I am missing something, but... how can you say that it works if it omits to test the last item? Time later, driving to home and still thinking about this routine, I finally recalled what you wanted to say with comprobation. Yes, you are right - your code works. If I would have payed more attention to the routine, I would have noticed. But, stupidly, I concentrated only on the cycle, noting that it was missing a test on the last item. That last item is managed by the last test before exiting. Still I don't like this routine. What happens if TabStrip1.Count=0 (emtpy tabstrip)? Ouch! TabStrip without tabs doesn't fit in my mind, ie Why somebody want a TabStrip without at least one tab? Moreover, by default TabStrip have one tab. (design time and execution time). Listen twice before you speak. This is why we have two ears, but only one mouth. ha! Very funny. I like it. Regards. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
[Gambas-user] static const?
Hi everybody. Well, all us knows that a constant is something that can't change. Then, constants would be class members. So, when a class is instantiated, constants should be shared by all instances. The online help exclude the use of STATIC keyword in the declaration of constants, so the STATIC keyword would be innecesary. Is this really the case or is it necessary to declare the constants by the STATIC keyword? (STATIC [PUBLIC | PRIVATE] CONST) -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Hi everybody. Well, all us knows that a constant is something that can't change. Then, constants would be class members. So, when a class is instantiated, constants should be shared by all instances. The online help exclude the use of STATIC keyword in the declaration of constants, so the STATIC keyword would be innecesary. Is this really the case or is it necessary to declare the constants by the STATIC keyword? (STATIC [PUBLIC | PRIVATE] CONST) No STATIC with CONST. Or maybe the compiler is more tolerant than that? -- Benoît Minisini -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
No STATIC with CONST. Or maybe the compiler is more tolerant than that? Maybe the compiler is a too much good guy :) I think that the compiler shouldn't allow to do something like that: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer DIM a AS Integer = 0 DIM b AS Integer = 0 FOR a = 1 TO TabStrip3.Count STEP 1 IF TabStrip3[(a - 1)].Caption = IdCaption THEN b = a a = TabStrip3.Count RETURN a ENDIF NEXT END Someone thought that this code is good one. Leaving aside the obvious conceptual confusion of the author, and that the routine doesn't do what it claims, it is important to note that it is possible to change the variable that controls the FOR structure, and included the return statement inside the loop. I think the compiler should not allow these things, at least for mercy through the eyes of those who are finally forced to read code like this. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
No STATIC with CONST. Or maybe the compiler is more tolerant than that? Maybe the compiler is a too much good guy :) I think that the compiler shouldn't allow to do something like that: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer DIM a AS Integer = 0 DIM b AS Integer = 0 FOR a = 1 TO TabStrip3.Count STEP 1 IF TabStrip3[(a - 1)].Caption = IdCaption THEN b = a a = TabStrip3.Count RETURN a ENDIF NEXT END Someone thought that this code is good one. Leaving aside the obvious conceptual confusion of the author, and that the routine doesn't do what it claims, it is important to note that it is possible to change the variable that controls the FOR structure, and included the return statement inside the loop. I think the compiler should not allow these things, at least for mercy through the eyes of those who are finally forced to read code like this. Why shouldn't the compiler allow to modify a loop variable? It is sometimes useful. Why shouldn't the compiler allow to return from inside a loop? It is perfectly valid to do that. A bad programmer using some syntax for writing bad code does not necessary imply that that syntax should be forbidden. Regards, -- Benoît Minisini -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Generally bad code... What that supposed to do? Either it will return TabStrip3.Count or zero. This would do exactly same thing: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN RETURN TabStrip3.Count ENDIF NEXT END Jussi 2010/4/13 Fabián Flores Vadell fabianfloresvad...@gmail.com: No STATIC with CONST. Or maybe the compiler is more tolerant than that? Maybe the compiler is a too much good guy :) I think that the compiler shouldn't allow to do something like that: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer DIM a AS Integer = 0 DIM b AS Integer = 0 FOR a = 1 TO TabStrip3.Count STEP 1 IF TabStrip3[(a - 1)].Caption = IdCaption THEN b = a a = TabStrip3.Count RETURN a ENDIF NEXT END Someone thought that this code is good one. Leaving aside the obvious conceptual confusion of the author, and that the routine doesn't do what it claims, it is important to note that it is possible to change the variable that controls the FOR structure, and included the return statement inside the loop. I think the compiler should not allow these things, at least for mercy through the eyes of those who are finally forced to read code like this. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
I forgot Dim a as integer but you got the point. Jussi On Tue, Apr 13, 2010 at 22:29, Jussi Lahtinen jussi.lahti...@gmail.com wrote: Generally bad code... What that supposed to do? Either it will return TabStrip3.Count or zero. This would do exactly same thing: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN RETURN TabStrip3.Count ENDIF NEXT END Jussi 2010/4/13 Fabián Flores Vadell fabianfloresvad...@gmail.com: No STATIC with CONST. Or maybe the compiler is more tolerant than that? Maybe the compiler is a too much good guy :) I think that the compiler shouldn't allow to do something like that: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer DIM a AS Integer = 0 DIM b AS Integer = 0 FOR a = 1 TO TabStrip3.Count STEP 1 IF TabStrip3[(a - 1)].Caption = IdCaption THEN b = a a = TabStrip3.Count RETURN a ENDIF NEXT END Someone thought that this code is good one. Leaving aside the obvious conceptual confusion of the author, and that the routine doesn't do what it claims, it is important to note that it is possible to change the variable that controls the FOR structure, and included the return statement inside the loop. I think the compiler should not allow these things, at least for mercy through the eyes of those who are finally forced to read code like this. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Why shouldn't the compiler allow to modify a loop variable? It is sometimes useful. I'm refering to the loop FOR only. IMHO, WHILE and REPEAT are good structures that allow at programmer take absolute control over iterations, objective of FOR is iterate all items of a memory structure. At least, I think that was of the original design purpose (distorted after). In fact, the need of FOR structure is relative. Any need can be easily cover with WHILE and REPEAT. I don't see the need for break a iteration structure from inside, in any way (even break and continue). This would be done from conditional input or output of the structure. But I see the consecuences. May be, the exeption to this is FOR EACH structure. Why shouldn't the compiler allow to return from inside a loop? It is perfectly valid to do that. Why allow break a loop in this way? That often leads to write multiple statements RETURN in a function. That does not comply with the theorem of structured programming (that have as one of its premises allow only a input point and unique exit). I think that in practice this difficults the tests; if necesary to port the code, this could be an aditional problem; among other things. A bad programmer using some syntax for writing bad code does not necessary imply that that syntax should be forbidden. I agree, but actually I was thinking that this affect more to those who approach programming in an informal way. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
2010/4/13 Jussi Lahtinen jussi.lahti...@gmail.com: I forgot Dim a as integer but you got the point. Jussi Yes Jussi. But my point isn't to do that the code work, it's show a bad use of language resources. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
First you referred to FOR loop only, but with case of return command you are talking more generally about loops? Or so I understand as you are speaking about it's influence to code structure. Consider this, if you have VERY long iteration and but you are done with first element of iteration. Then there is no reason to continue iteration anymore, because it is just waste of time. Let's take your example (I did clean it up): PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN RETURN TabStrip3.Count ENDIF NEXT RETURN 0 END Now this is not very realistic case with this example, but let's pretend it is so. Let's say that this iteration takes 10 second to run trough and there are 10 items. When first item is what is needed, then this function takes only 1 second to execute. If we do not break that loop it will always take 10 seconds. Just to make sure, you meant it should be like this? PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer Dim b as Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN b = TabStrip3.Count ENDIF NEXT RETURN b END Also you should notice, that this is normal practice in Basic languages. And therefore also question of portability. Jussi 2010/4/14 Fabián Flores Vadell fabianfloresvad...@gmail.com: Why shouldn't the compiler allow to modify a loop variable? It is sometimes useful. I'm refering to the loop FOR only. IMHO, WHILE and REPEAT are good structures that allow at programmer take absolute control over iterations, objective of FOR is iterate all items of a memory structure. At least, I think that was of the original design purpose (distorted after). In fact, the need of FOR structure is relative. Any need can be easily cover with WHILE and REPEAT. I don't see the need for break a iteration structure from inside, in any way (even break and continue). This would be done from conditional input or output of the structure. But I see the consecuences. May be, the exeption to this is FOR EACH structure. Why shouldn't the compiler allow to return from inside a loop? It is perfectly valid to do that. Why allow break a loop in this way? That often leads to write multiple statements RETURN in a function. That does not comply with the theorem of structured programming (that have as one of its premises allow only a input point and unique exit). I think that in practice this difficults the tests; if necesary to port the code, this could be an aditional problem; among other things. A bad programmer using some syntax for writing bad code does not necessary imply that that syntax should be forbidden. I agree, but actually I was thinking that this affect more to those who approach programming in an informal way. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Aaa I think you meant it this way: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer Dim b as Integer REPEAT IF TabStrip3[a].Caption = IdCaption THEN b = TabStrip3.Count BREAK ENDIF WHILE a TabStrip3.Count RETURN b END Jussi On Wed, Apr 14, 2010 at 01:55, Jussi Lahtinen jussi.lahti...@gmail.com wrote: First you referred to FOR loop only, but with case of return command you are talking more generally about loops? Or so I understand as you are speaking about it's influence to code structure. Consider this, if you have VERY long iteration and but you are done with first element of iteration. Then there is no reason to continue iteration anymore, because it is just waste of time. Let's take your example (I did clean it up): PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN RETURN TabStrip3.Count ENDIF NEXT RETURN 0 END Now this is not very realistic case with this example, but let's pretend it is so. Let's say that this iteration takes 10 second to run trough and there are 10 items. When first item is what is needed, then this function takes only 1 second to execute. If we do not break that loop it will always take 10 seconds. Just to make sure, you meant it should be like this? PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer Dim b as Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN b = TabStrip3.Count ENDIF NEXT RETURN b END Also you should notice, that this is normal practice in Basic languages. And therefore also question of portability. Jussi 2010/4/14 Fabián Flores Vadell fabianfloresvad...@gmail.com: Why shouldn't the compiler allow to modify a loop variable? It is sometimes useful. I'm refering to the loop FOR only. IMHO, WHILE and REPEAT are good structures that allow at programmer take absolute control over iterations, objective of FOR is iterate all items of a memory structure. At least, I think that was of the original design purpose (distorted after). In fact, the need of FOR structure is relative. Any need can be easily cover with WHILE and REPEAT. I don't see the need for break a iteration structure from inside, in any way (even break and continue). This would be done from conditional input or output of the structure. But I see the consecuences. May be, the exeption to this is FOR EACH structure. Why shouldn't the compiler allow to return from inside a loop? It is perfectly valid to do that. Why allow break a loop in this way? That often leads to write multiple statements RETURN in a function. That does not comply with the theorem of structured programming (that have as one of its premises allow only a input point and unique exit). I think that in practice this difficults the tests; if necesary to port the code, this could be an aditional problem; among other things. A bad programmer using some syntax for writing bad code does not necessary imply that that syntax should be forbidden. I agree, but actually I was thinking that this affect more to those who approach programming in an informal way. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Always forgetting something... INC a. Jussi On Wed, Apr 14, 2010 at 01:59, Jussi Lahtinen jussi.lahti...@gmail.com wrote: Aaa I think you meant it this way: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer Dim b as Integer REPEAT IF TabStrip3[a].Caption = IdCaption THEN b = TabStrip3.Count BREAK ENDIF WHILE a TabStrip3.Count RETURN b END Jussi On Wed, Apr 14, 2010 at 01:55, Jussi Lahtinen jussi.lahti...@gmail.com wrote: First you referred to FOR loop only, but with case of return command you are talking more generally about loops? Or so I understand as you are speaking about it's influence to code structure. Consider this, if you have VERY long iteration and but you are done with first element of iteration. Then there is no reason to continue iteration anymore, because it is just waste of time. Let's take your example (I did clean it up): PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN RETURN TabStrip3.Count ENDIF NEXT RETURN 0 END Now this is not very realistic case with this example, but let's pretend it is so. Let's say that this iteration takes 10 second to run trough and there are 10 items. When first item is what is needed, then this function takes only 1 second to execute. If we do not break that loop it will always take 10 seconds. Just to make sure, you meant it should be like this? PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer Dim b as Integer FOR a = 0 TO TabStrip3.Count - 1 IF TabStrip3[a].Caption = IdCaption THEN b = TabStrip3.Count ENDIF NEXT RETURN b END Also you should notice, that this is normal practice in Basic languages. And therefore also question of portability. Jussi 2010/4/14 Fabián Flores Vadell fabianfloresvad...@gmail.com: Why shouldn't the compiler allow to modify a loop variable? It is sometimes useful. I'm refering to the loop FOR only. IMHO, WHILE and REPEAT are good structures that allow at programmer take absolute control over iterations, objective of FOR is iterate all items of a memory structure. At least, I think that was of the original design purpose (distorted after). In fact, the need of FOR structure is relative. Any need can be easily cover with WHILE and REPEAT. I don't see the need for break a iteration structure from inside, in any way (even break and continue). This would be done from conditional input or output of the structure. But I see the consecuences. May be, the exeption to this is FOR EACH structure. Why shouldn't the compiler allow to return from inside a loop? It is perfectly valid to do that. Why allow break a loop in this way? That often leads to write multiple statements RETURN in a function. That does not comply with the theorem of structured programming (that have as one of its premises allow only a input point and unique exit). I think that in practice this difficults the tests; if necesary to port the code, this could be an aditional problem; among other things. A bad programmer using some syntax for writing bad code does not necessary imply that that syntax should be forbidden. I agree, but actually I was thinking that this affect more to those who approach programming in an informal way. -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
2010/4/13 Jussi Lahtinen jussi.lahti...@gmail.com: Aaa I think you meant it this way: PUBLIC FUNCTION ScanTab(IdCaption AS Integer) AS Integer Dim a as Integer Dim b as Integer REPEAT IF TabStrip3[a].Caption = IdCaption THEN b = TabStrip3.Count BREAK ENDIF WHILE a TabStrip3.Count RETURN b END Jussi You're getting close. But, I think that is no need to break the loop using the BREAK sentence. Just you must find the right condition to the loop. I don't refer to that example anymore, because is easier explain it in a more abstract level: REPEAT 'do something UNTIL cond1 OR (cond2 AND cond3) ... WHILE cond1 AND cond2 OR cond3 'do something WEND Where one of the above conditions (condX) is that usually is write inside the loop to allow the BREAK or CONTINUE sentence (or RETURN). Just in case: REPEAT b = TabStrip3.Count ' In fact, this does nothing usefull INC a UNTIL a TabStrip3.Count OR TabStrip3[a].Caption = IdCaption -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
Just in case: REPEAT b = TabStrip3.Count ' In fact, this does nothing usefull INC a UNTIL a TabStrip3.Count OR TabStrip3[a].Caption = IdCaption This doesn't make same functionality. Because if ldCaption doesn't match to any of tabstrip captions, function will still answer TabStrip3.Count instead of zero. In short, you cannot remove IF THEN construct. I think I have done enough errors for this day (I'm going to sleep). Jussi -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
Re: [Gambas-user] static const?
2010/4/13 Jussi Lahtinen jussi.lahti...@gmail.com: Just in case: REPEAT b = TabStrip3.Count ' In fact, this does nothing usefull INC a UNTIL a TabStrip3.Count OR TabStrip3[a].Caption = IdCaption This doesn't make same functionality. That is why I did not want to follow the example anymore. This function never had has any functionality, due to their errors. Neither, your version of the function, because it returns TabStrip3.Count which is the amount of tabs containing the control, ie always return the same value. Because if ldCaption doesn't match to any of tabstrip captions, function will still answer TabStrip3.Count instead of zero. In short, you cannot remove IF THEN construct. Put it out of loop. The correct code: PRIVATE FUNCTION ScanTab(IdCaption AS String) AS Byte DIM a AS Byte = 0 WHILE (a TabStrip1.Count - 1) AND (TabStrip1[a].Text IdCaption) INC a WEND RETURN IF(TabStrip1[a].Caption = IdCaption, a, -1) END I think I have done enough errors for this day (I'm going to sleep). Sweet dreams (my childs are going to sleep right now, too). -- Fabián Flores Vadell www.speedbooksargentina.blogspot.com -- Download Intel#174; Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev ___ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
