Re: [fpc-devel] New feature discussion: LAMBDA
Jeff Wormsley wrote: One of the reasons I like Pascal is that you do usually have to spell out what you are doing. It makes reading the code months or years later, or reading someone else's code much easier. That is why I never use with. For me with severely brakes the paradigm you state. -Michael ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
Jeff Wormsley wrote: Wow, talk about unreadable code... In fact I did not ever try to understand this. I just happened to know about Lambda in Prism and wanted to let the forum share that. I'm all for saving typing, but not at the expense of readability. Agreed. This reminds me of C's oddball ? operator. In fact I think that the ? operator in C is easily readable (But of course in C you easily can create unreadable code by e.g. doing assignments in if-clauses. if (a=b) a=1; which happens to translate in Pascal as: a:=b; if a0 then a:=1; -Michael ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
Jeff Wormsley pisze: Michael Schnell wrote: Again something inspired by Delphi-Prism ? ( http://prismwiki.codegear.com/en/Lambda_Expressions ) Wow, talk about unreadable code... why all vote about something, that wasn't proposed ? -- Darek ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
[fpc-devel] New feature discussion: LAMBDA
Hi Based on discussion about for in I want to suggest my proposition. When we investigate some code, sometimes we found pattern: Pattern 1: / begin startfun; try ... finally stopfun; end; / end; Pattern 2: for i:= startfun to stopfun do begin end; Pattern 3: startfun; while stopfun do begin ... end; Common for all mentioned patterns are two connected functions, which controlled running of body source. First make all initializations, second helping with iterations and finalizations. My proposition is make possibility of join, those pair to one sentence. All patterns can be change to one common template: if startfun then repeat until stopfun; I You see we need two function with boolean result. Of course possibility of parameters give wide appliance. To preserve pascalish style I propose something like this: tMyObject = class(tObject) function startfun:boolean; function stopfun:boolean; property lambdafun; start startfun stop stopfun; end; and invoke: var t : tMyObject; begin .. t.lambdafun do begin end; end; because on declaration side is similar do properties (also two function) we can use the same syntax. Only keyword start and stop exchange read and write. To using i thought about WITH, but it may confusing bit, thus I propose omit, and only use keyword DO. Why lambda. Because is very similar to constructing no name procedures and use them as normal. We have few mechanism controlling runnig: IF, REPEAT, WHILE, FOR. They work well, but sometimes they are week. For example we don't have enough primitives do build own implementation FORIN method, on iterators also. But in Lisp any mechanism, any sequence of computing collection can be done and source is very readable lisp syntax: (lambda (formal parameters) body) This is not unusual, but we can send this declaration as argument of procedure. Of course syntax like this tlist.foreach( procedure (x : tObject);begin writeln(x) end) is ugly (thought I sow something similar in C++/boost) but when we change it a bit: tlist.foreach(x) do begin writeln(x); end; its not so strange Because my english is very poor I only show some application EXP. mutex (and patterns as RIAA) tMutex = class property makeatomic; start lock stop unlock; end; . begin tMutex.makeatomic do begin ... end; end; EXP: foreach tMyList = class function tMyList.start:boolean; begin current:=first; result:=currentnil; end; function tMyList.stop:boolean; begin current:=next(current); resutl:=currentnil; end; When attributes are added, or exception caching this will be more flexible. -- Darek ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
Again something inspired by Delphi-Prism ? ( http://prismwiki.codegear.com/en/Lambda_Expressions ) -Michael ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
Michael Schnell pisze:
Again something inspired by Delphi-Prism ?
( http://prismwiki.codegear.com/en/Lambda_Expressions )
No at all, I don't even see this before. I thing long about this. But
lately I see this in C++ (strange) and Lisp (beautiful)
In Prism have You:
c - c.Name = 'Smith'
which is very strange, special syntax, and need to be translate to method, and declaration longer
than one line is awful,
my proposition semantically is between properties (they consist also two function),
aspect programming and lambda
is very easy to translate to ordinal pascal( lambda invoke change to
repeat-while iteration,
similarly as in generics)
has wider application:
from FPC WIKI:
procedure StringLoop(S: String);
var
C: Char;
begin
for C in S do
DoSomething(C);
end;
my prop:
procedure stringloop(s :tMyString);
begin
{with} s.eachword do begin
if s.currentword'begin' then
writeln(s.currentword);
end;
end;
of course I can write
procedure stringloop(s :tMyString);
begin
s.firstWord;
try
while s.nexword do begin
if s.currentword'begin' then
writeln(s.currentword);
end;
except
s.exceptWord;
end;
end;
which can be equivalent
from compiler side invoke of lambda is translate to proper iteration before
main compilation
from developer side: its easy to use as properties,
fewer bugs caused forget of initialization or finalization, or use incompatible init and step
function in iterators
--
Darek
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Re: [fpc-devel] New feature discussion: LAMBDA
Michael Schnell wrote: Again something inspired by Delphi-Prism ? ( http://prismwiki.codegear.com/en/Lambda_Expressions ) Wow, talk about unreadable code... I'm all for saving typing, but not at the expense of readability. This reminds me of C's oddball ? operator. One of the reasons I like Pascal is that you do usually have to spell out what you are doing. It makes reading the code months or years later, or reading someone else's code much easier. So it might not be the most efficient in terms of typing, or even compilation or execution, but the savings in maintenance more than make up for it. The examples given at that site would drive me crazy. I don't believe I'll be using Prism any time soon. Jeff. -- I haven't smoked for 3 years, 2 months and 3 days, saving $5,222.69 and not smoking 34,817.99 cigarettes. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
Pascal have something close to lambda, and it's nested functions/procedures
The original idea of lambda is to have sub process that takes parameters and
simple tasks.
For example (in Ruby):
def action(base)
expo = lambda { |by_num| base ** by_num}
x = something
a = expo(x)
end
I can do the same with the following:
procedure action(base : integer)
function expo(by_num)
begin
expo := base ** by_num
end;
var x,a : integer;
begin
x := something;
a := expo(x);
...
end;
Of curse it's one usage for it, but most of the real usage of lambda can be
made in pascal today. And please do not take ideas from C++, it's a language
that wrote on it's agenda to implement any possible technology out there
regardless of it's need or usage, and it's impossible to use that language
without some framework or ignoring this technologies.
Ido
http://ik.homelinux.org/
2009/10/20 Dariusz Mazur dar...@emadar.com
Michael Schnell pisze:
Again something inspired by Delphi-Prism ?
( http://prismwiki.codegear.com/en/Lambda_Expressions )
No at all, I don't even see this before. I thing long about this. But
lately I see this in C++ (strange) and Lisp (beautiful)
In Prism have You:
c - c.Name = 'Smith'
which is very strange, special syntax, and need to be translate to
method, and declaration longer than one line is awful,
my proposition semantically is between properties (they consist also two
function), aspect programming and lambda
is very easy to translate to ordinal pascal( lambda invoke change to
repeat-while iteration,
similarly as in generics)
has wider application:
from FPC WIKI:
procedure StringLoop(S: String);
var
C: Char;
begin
for C in S do
DoSomething(C);
end;
my prop:
procedure stringloop(s :tMyString);
begin
{with} s.eachword do begin
if s.currentword'begin' then
writeln(s.currentword);
end;
end;
of course I can write
procedure stringloop(s :tMyString);
begin
s.firstWord;
try
while s.nexword do begin
if s.currentword'begin' then
writeln(s.currentword);
end;
except
s.exceptWord;
end; end;
which can be equivalent
from compiler side invoke of lambda is translate to proper iteration before
main compilation
from developer side: its easy to use as properties, fewer bugs caused
forget of initialization or finalization, or use incompatible init and step
function in iterators
--
Darek
___
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___
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Re: [fpc-devel] New feature discussion: LAMBDA
In our previous episode, Jeff Wormsley said: ( http://prismwiki.codegear.com/en/Lambda_Expressions ) Wow, talk about unreadable code... I'm all for saving typing, but not at the expense of readability. This reminds me of C's oddball ? operator. (hmm, if I would name one feature I hate about C, that would be that if (x=y) goes unnoticed while legal. At least the ? operator doesn't bite you if you don't use it) ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
Marco van de Voort schreef: (hmm, if I would name one feature I hate about C, that would be that if (x=y) goes unnoticed while legal. At least the ? operator doesn't bite you if you don't use it) Off topic. Vincent ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
2009/10/20 Jeff Wormsley dawor...@comcast.net: ( http://prismwiki.codegear.com/en/Lambda_Expressions ) Wow, talk about unreadable code... +1 That's all I can say. -- Regards, - Graeme - ___ fpGUI - a cross-platform Free Pascal GUI toolkit http://opensoft.homeip.net/fpgui/ ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] New feature discussion: LAMBDA
ik pisze:
Pascal have something close to lambda, and it's nested
functions/procedures
The original idea of lambda is to have sub process that takes
parameters and simple tasks.
You don't understand me. I know sub process, this is nice feature of
pascal, but i talk about something different.
Sometimes we have sub process and want to do with them rather
complicated task.
For example (in Ruby):
def action(base)
expo = lambda { |by_num| base ** by_num}
x = something
a = expo(x)
end
I can do the same with the following:
procedure action(base : integer)
function expo(by_num)
begin
expo := base ** by_num
end;
var x,a : integer;
begin
x := something;
a := expo(x);
...
end;
My example was different. Try to implement my example with the same
readability, error prove,
Of curse it's one usage for it, but most of the real usage of lambda
can be made in pascal today. And please do not take ideas from C++,
it's a language that wrote on it's agenda to implement any possible
technology out there regardless of it's need or usage, and it's
impossible to use that language without some framework or ignoring
this technologies.
I don't draw from C++, which is imperative language , rather try to use
some of the best of functional language.
I don't even know, that it should be name lambda. Its similar to
iterators, but also to aspect. It has the same syntax as properties.
thats all.
2009/10/20 Dariusz Mazur dar...@emadar.com mailto:dar...@emadar.com
Michael Schnell pisze:
Again something inspired by Delphi-Prism ?
( http://prismwiki.codegear.com/en/Lambda_Expressions )
No at all, I don't even see this before. I thing long about this.
But lately I see this in C++ (strange) and Lisp (beautiful)
In Prism have You:
c - c.Name = 'Smith'
which is very strange, special syntax, and need to be translate to
method, and declaration longer than one line is awful,
my proposition semantically is between properties (they consist
also two function), aspect programming and lambda
is very easy to translate to ordinal pascal( lambda invoke change
to repeat-while iteration,
similarly as in generics)
has wider application:
from FPC WIKI:
procedure StringLoop(S: String);
var
C: Char;
begin
for C in S do
DoSomething(C);
end;
my prop:
procedure stringloop(s :tMyString);
begin
{with} s.eachword do begin
if s.currentword'begin' then
writeln(s.currentword);
end;
end;
of course I can write
procedure stringloop(s :tMyString);
begin
s.firstWord;
try
while s.nexword do begin
if s.currentword'begin' then
writeln(s.currentword);
end;
except
s.exceptWord;
end; end;
which can be equivalent
from compiler side invoke of lambda is translate to proper
iteration before main compilation
from developer side: its easy to use as properties, fewer bugs
caused forget of initialization or finalization, or use
incompatible init and step
function in iterators
--
Darek
___
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