Re: ElementType!(Range) problem
--Philippe wrote:: ElementType acts on types. It takes a type and 'returns' (compiles to, actually) another type. You need to give it typeof(listR). Then, as ElementType!(typeof(listR)) is a type, you cannot pass it to writeln. Use .stringof to go from the type to a string representation of its name. So: writefln(%s, ElementType!(typeof(listR)).stringof); ElementType!(typeof(listR)) is a type like any other. You can create a variable with it: ElementType!(typeof(listR)) elem; Got it!. Thanks. I faced this confusion because of the description for ElementType which is available in http://d-programming-language.org/phobos/std_range.html. It says, template ElementType(R): The element type of R. R does not have to be a range. The element type is determined as the type yielded by r.front for an object r or type R. For example, ElementType!(T[]) is T. If R is not a range, ElementType!R is void. So I thought that just passing ElementType!listR was adequate. :s
error Not the start of the UTF-8 sequence
Hello,
I get this error message:
Not the start of the UTF-8 sequence
without any other comment module name or whatnot.
This happens when I just added toString to the following struct, and used it:
struct Node {
// Note: level is equal to the number of chars up to this node.
// Note: a 'path' node without entry has key=.
char ch;
uint level;
Key key;
Value value;
...
string toString() {
if (this.key != )
return format(%s %s:%s, this.ch, this.key, this.value);
else
return format(%s, this.ch);
}
}
Hints? I'm blocked :-(
Denis
--
_
vita es estrany
spir.wikidot.com
Re: error Not the start of the UTF-8 sequence
spir Wrote:
Hello,
I get this error message:
Not the start of the UTF-8 sequence
without any other comment module name or whatnot.
This happens when I just added toString to the following struct, and used it:
struct Node {
// Note: level is equal to the number of chars up to this node.
// Note: a 'path' node without entry has key=.
char ch;
uint level;
Key key;
Value value;
...
string toString() {
if (this.key != )
return format(%s %s:%s, this.ch, this.key, this.value);
else
return format(%s, this.ch);
}
}
Hints? I'm blocked :-(
Denis
--
_
vita es estrany
spir.wikidot.com
struct Node {
// Note: level is equal to the number of chars up to this node.
// Note: a 'path' node without entry has key=.
dchar ch;
[SOLVED] [BUG?] Re: error Not the start of the UTF-8 sequence
On 04/06/2011 11:53 AM, Kagamin wrote:
spir Wrote:
Hello,
I get this error message:
Not the start of the UTF-8 sequence
without any other comment module name or whatnot.
This happens when I just added toString to the following struct, and used it:
struct Node {
// Note: level is equal to the number of chars up to this node.
// Note: a 'path' node without entry has key=.
char ch;
uint level;
Key key;
Value value;
...
string toString() {
if (this.key != )
return format(%s %s:%s, this.ch, this.key, this.value);
else
return format(%s, this.ch);
}
}
Hints? I'm blocked :-(
struct Node {
// Note: level is equal to the number of chars up to this node.
// Note: a 'path' node without entry has key=.
dchar ch;
Sorry, no, nothing to do with the type. The error came from a special case
where ch='\0'. Seems some routine in dmd does not like that; but no idea where
the error comes from.
There are two points to solve, I guess:
* The error message should tell where it happens.
* '\0' is a valid code point, should pass through without error.
Denis
--
_
vita es estrany
spir.wikidot.com
template alias parameters
Hi,
I'm playing around with template alias parameters. At the moment I'm
considering the following simple code:
struct A
{};
struct B( T )
{
T t;
};
struct C( alias T )
{
T t;
};
void main()
{
B!A a;
C!A b;
}
What exactly is the difference between a and b? Both seem to do the same
thing but obviously there is a difference as I cannot instanciate C with
buildin types as template parameter (C!int c results in Error:
template instance C!(int) does not match template declaration C(alias T)).
The other question is: is there a possibility to distinguinish between
different things passed to a template alias paramter? - Like isType,
isVariable, isLiteral, isTemplate ...
enuhtac
Re: incompatible types!
On 06.04.2011 02:15, Steven Schveighoffer wrote: On Tue, 05 Apr 2011 19:37:15 -0400, Caligo iteronve...@gmail.com wrote: It's just frustrating, that's all. Writing thousands of lines of code and having everything stop because of a compiler bug is just frustrating. I completely understand. It's why I have to periodically stop using D. Dcollections sat idle for over a year while I waited for a compiler bug to be fixed. I know progress is being made, and all that is appreciated. But, I don't remember ever hearing anything about D2 being in beta. If anything, I remember months ago where D2 was recommended for new projects. So, now I'm not sure what I'm supposed to do. Start all over again from scratch? I really like my design, so I guess I'll have to wait till it gets fixed. Sorry you got that impression. The fact is, as long as you are using the non-broken features, D2 is pretty useful, even downright awesome :) The issue is, if you hit one of those broken ones. Unfortunately, the release of TDPL didn't make all those features magically appear fully implemented. So since TDPL is promoted as the offical language spec, D2 suddenly jumped way back in the release cycle, since many of its unimplemented/not-fully-implemented features became official. I'd highly recommend *NOT* to use D2 for new projects unless you are willing to redesign your code to work around those issues, or wait for them to be fixed. I truly wish this wasn't the case, but I don't see how anyone can confidently recommend D2 for professional or non-toy projects. This may sound like an anti-endorsement, but I assure you it is not. I think D2 is going to be absolutely killer when it's finished. I just would not use it for professional development *right now*, where deadlines and budgets are under consideration. If you can afford to put it down when it breaks and wait for a fix, then I think it will be worth the wait. -Steve Both the d1 and d2 homepage states the following: There are two versions of the language: 1. D version 1 which is in maintenance mode. 2. D version 2 which is recommended for new projects. Should it mention that d2 is beta and phobos alpha? Or are you alone in thinking that?
Why doesn't curry work with multiple arguments?
import std.functional;
void foo(int x, int y, int z)
{
}
alias curry!(foo, 1, 2, 3) bar;
Error: template instance curry!(foo,1,2,3) does not match template declaration
curry(alias fun,alias arg)
Shouldn't curry take a variable number of arguments and then check the length
of the arguments passed in against `fun`s length of parameters, and do its work
from there?
I'm trying to translate a C header file from the following to a D equivalent:
#define txmOpenFile(hwndTV, szFile) \
SendMessage((hwndTV), TXM_OPENFILE, 0, (LPARAM)(szFile))
Yes, I write a whole new function, but why do that when curry is there. Or so I
thought..
Re: Why doesn't curry work with multiple arguments?
Andrej Mitrovic Wrote: Yes, I write a whole new function, but why do that when curry is there. Or so I thought.. Oops: *Yes, I _can_ write a whole new function
Re: Why doesn't curry work with multiple arguments?
Here's a basic implementation:
import std.stdio;
import std.traits;
import std.metastrings;
template count(T...)
{
enum count = T.length;
}
template curry(alias fun, args...)
{
static if (args.length (ParameterTypeTuple!fun).length)
{
static assert(0, Format!(Tried to pass %s arguments, max is %s.,
count!args, (ParameterTypeTuple!fun).length));
}
static if (is(typeof(fun) == delegate) || is(typeof(fun) == function))
{
ReturnType!fun curry()
{
return fun(args);
}
}
}
void foo(int x, int y)
{
writeln(x, y);
}
alias curry!(foo, 1, 2) bar;
void main()
{
bar();
}
It will complain if you try to pass it more arguments than a function
can take. I didn't implement curry's original else clause because I
have no idea what's going on there (some comments would be useful in
Phobos implementations, people!..)
There is some wacky error if I didn't use the count template
workaround. If I try to use args.length twice, like so:
static if (args.length (ParameterTypeTuple!fun).length)
{
static assert(0, Format!(Tried to pass %s arguments, max is %s.,
args.length, (ParameterTypeTuple!fun).length));
}
Then I get back: identifier 'length' of 'args.length' is not defined
But it only errors out in the static assert, and yet it can check
args.length in the static if. Really weird.
Re: Why doesn't curry work with multiple arguments?
Crap, that is a horrible implementation, I didn't take into account not binding all arguments. Be right back..
Re: Why doesn't curry work with multiple arguments?
Ok, enjoy this monstrosity:
template count(T...)
{
enum count = T.length;
}
template myCurry(alias fun, args...)
{
static if (args.length (ParameterTypeTuple!fun).length)
{
static assert(0, Format!(Tried to pass %s arguments, max is %s.,
count!args, (ParameterTypeTuple!fun).length));
}
static if (is(typeof(fun) == delegate) || is(typeof(fun) == function))
{
static if ((ParameterTypeTuple!fun).length - count!args)
{
ReturnType!fun myCurry(ParameterTypeTuple!fun[0 ..
(ParameterTypeTuple!fun).length - count!args] myarg)
{
return fun(args, myarg);
}
}
else
{
ReturnType!fun myCurry()
{
return fun(args);
}
}
}
}
Re: Why doesn't curry work with multiple arguments?
It's still wrong, the tuple is backwards. Haha, that's what I get for not unittesting.
Re: Why doesn't curry work with multiple arguments?
Andrej Mitrovic: Here's a basic implementation: I have some general comments: - Currying and partial function application are not exactly the same thing. So I am not sure the curry in std.functional is named correctly; - Partial application is important in a language that wants to support functional idioms a little. This means that if D doesn't currently supports Partial application well, then it's worth improving; - A good function application must be able to solve this little rosettacode task too: http://rosettacode.org/wiki/Partial_function_application Bye, bearophile
Re: Why doesn't curry work with multiple arguments?
Wow, talk about enlightement. I think I've done it now:
import std.stdio;
import std.traits;
import std.metastrings;
template count(T...)
{
enum count = T.length;
}
template myCurry(alias fun, args...)
{
static if (args.length (ParameterTypeTuple!fun).length)
{
static assert(0, Format!(Tried to pass %s arguments, max is %s.,
count!args, (ParameterTypeTuple!fun).length));
}
ReturnType!fun myCurry(T...)(T t)
{
return fun(args, t);
}
}
void foo(string x, int y, int z)
{
writeln(x, y, z);
}
alias myCurry!(foo, bar) oneCurry;
alias myCurry!(foo, bar, 1)twoCurry;
alias myCurry!(foo, bar, 1, 2) threeCurry;
void main()
{
oneCurry(1, 2);
twoCurry(2);
threeCurry();
}
Re: Why doesn't curry work with multiple arguments?
On 4/6/11, bearophile bearophileh...@lycos.com wrote: - Currying and partial function application are not exactly the same thing. So I am not sure the curry in std.functional is named correctly; Maybe bind should be a better name. I'm not sure..
Re: Why doesn't curry work with multiple arguments?
Andrej Mitrovic: Maybe bind should be a better name. I'm not sure.. In Python there is something similar that's named partial: http://docs.python.org/library/functools.html#functools.partial Bye, bearophile
Re: Why doesn't curry work with multiple arguments?
Well this still hasn't solved my problem. Because I shouldn't bind
from left to right, but arbitrarily.
So ideally I would want this:
void foo(string str, int x, int y, string str2) { }
alias bind!(foo, null, 1, 2, null) twoStrings;
twoStrings(abc, def); - foo(abc, 1, 2, def);
I'm pretty sure I could do this with D's templates.
char[][] join == string
Given an array of strings std.string.join() returns a single string:
import std.string;
void main() {
string[] a1 = [hello, red];
string j1 = join(a1, ); // OK
}
But in a program I need an array of mutable arrays of chars. If I join the
arrays I get a mutable array of chars. But I need a string:
import std.string;
void main() {
char[][] a2 = [hello.dup, red.dup];
string j2 = join(a2, ); // error
}
Error: cannot implicitly convert expression (join(a, )) of type char[] to
string
.idup avoids the error:
string j3 = join(a2, ).idup; // OK
Given the low efficiency of the D GC it's better to reduce memory allocations
as much as possible.
Here join() creates a brand new array, so idup performs a useless copy. To
avoid this extra copy do I have to write another joinString() function?
Bye,
bearophile
Re: char[][] join == string
On 04/06/2011 05:13 PM, bearophile wrote:
Given an array of strings std.string.join() returns a single string:
import std.string;
void main() {
string[] a1 = [hello, red];
string j1 = join(a1, ); // OK
}
But in a program I need an array of mutable arrays of chars. If I
join the arrays I get a mutable array of chars. But I need a string:
Tangentially off-topic: This does not apply to your case, but I think we
should think twice before deciding that we need a string. For example,
functions parameters should be const(char[]) (or const(char)[]) instead
of string as that type accepts both mutable and immutable strings.
import std.string;
void main() {
char[][] a2 = [hello.dup, red.dup];
string j2 = join(a2, ); // error
If possible, this might work:
const(char[]) j2 = join(a2, );
There is also std.exception.assumeUnique, but it's too eager to be safe
and tries to null its parameter and this fails:
string j2 = assumeUnique(join(a2, )); // error
Finally, casting ourselves works:
string j2 = cast(string)join(a2, );
}
Error: cannot implicitly convert expression (join(a, )) of type
char[] to string
..idup avoids the error:
string j3 = join(a2, ).idup; // OK
Given the low efficiency of the D GC it's better to reduce memory
allocations as much as possible.
Here join() creates a brand new array, so idup performs a useless
copy. To avoid this extra copy do I have to write another joinString()
function?
Bye,
bearophile
Ali
Re: template alias parameters
enuhtac Wrote:
Hi,
I'm playing around with template alias parameters. At the moment I'm
considering the following simple code:
struct A
{};
struct B( T )
{
T t;
};
struct C( alias T )
{
T t;
};
void main()
{
B!A a;
C!A b;
}
What exactly is the difference between a and b? Both seem to do the same
No difference.
thing but obviously there is a difference as I cannot instanciate C with
buildin types as template parameter (C!int c results in Error:
template instance C!(int) does not match template declaration C(alias T)).
I'm going to take a guess at the issue here. alias parameters are supposed to
bind to a symbol. Types aren't symbols, they aren't things that will have an
address during runtime. I'm not exactly sure why the struct is excepted.
The other question is: is there a possibility to distinguinish between
different things passed to a template alias paramter? - Like isType,
isVariable, isLiteral, isTemplate ...
enuhtac
There isn't a distinction for literal vs variable. I'm pretty sure. As
mentioned you don't pass types to alias. And you probably wouldn't write a
template that accepts a template or a variable.
As it is a symbol you do get to use typeof() and the likes on it.
