Re: Why doesn't this work in D2?
On 2010-06-28 02:28, BCS wrote:
Hello Jacob,
That's annoying, specially since char is a value type. I would
preferably have a solution for both D1 and D2. Can I use a template to
cast/alias away the immutable part?
One solution would be to have templates strip off const/immutable from
the top level of args.
void F1(T)(T t) { pragam(msg,typeof(t).stringof); }
string s1;
immutable(char[]) s2
char[] s3
F1(s1); // immutable(char)[] // all as normal
F1(s2); // immutable(char)[] // making a mutable copy of a immutable
value is OK
F1(s3); // char[] // all as normal
void F2(T)(immutable T t) { pragam(msg,typeof(t).stringof); }
F2(s1); // immutable(char[]) // making an immutable copy of a mutable
reference to immutable data is ok
F2(s2); // immutable(char[]) // all as normal
F2(s3); // error, invalid conversion
This solution would match the proposal that popped up a while ago to
allow value assignment from const/immutable to mutable.
I don't think I understand what you're showing here. How would I strip
off the const/immutable with a template ?
--
/Jacob Carlborg
Re: Why doesn't this work in D2?
On Mon, Jun 28, 2010 at 10:56, Jacob Carlborg d...@me.com wrote:
Something to keep in mind: as of 2.04x (.045? maybe), the way UTF-8 / UTF-32
is managed was changed. asd is an array of immutable(dchar), not
imutable(char). At least DMD tells me that its element type is 'dchar'.
So your function can be done this way in D2:
void foo(T,U)(in T[] a, U b) if (is(U : Unqual!T)) // that compiles only if
b can be cast to A
{
writeln(a,b);
}
asd.foo('s'); // prints asds.
is(U == Unqual!T) does not work, for U is 'char' while Unqual!T is 'dchar'.
More generally, using ranges and not arrays, the template becomes a bit more
heavy:
void foo(Range,Elem)(in Range range, Elem elem)
if (isInputRange!Range is(Elem : Unqual!(ElementType!Range)))
{
...
}
I don't think I understand what you're showing here. How would I strip off
the const/immutable with a template ?
Hmmm...
* plays with is expressions *
This seems to work:
template UnConst(T)
{
static if (is(T t == const U, U)) // that is: 'if T is a 'const U', for
some U'
alias U UnConst; // then give me the U, (ie, T
without a const)
else
alias T UnConst; // else give me the (original)
T
}
template UnImmutable(T)
{
static if (is(T t == immutable U, U)) // 'if T is an 'immutable U', for
some U'
alias U UnImmutable;
else
alias T UnImmutable;
}
test:
void main() {
alias const int Int;
writeln(UnConst!Int.stringof);
writeln(Int.stringof);
writeln(UnConst!int.stringof);
writeln(UnConst!(const int).stringof);
writeln(UnConst!(immutable int).stringof);
alias immutable int IInt;
writeln(UnConst!IInt.stringof);
writeln(IInt.stringof);
writeln(UnImmutable!int.stringof);
writeln(UnImmutable!(const int).stringof);
writeln(UnImmutable!(immutable int).stringof);
}
Philippe
Re: Why doesn't this work in D2?
On Mon, 28 Jun 2010 08:14:12 -0400, Philippe Sigaud philippe.sig...@gmail.com wrote: On Mon, Jun 28, 2010 at 10:56, Jacob Carlborg d...@me.com wrote: Something to keep in mind: as of 2.04x (.045? maybe), the way UTF-8 / UTF-32 is managed was changed. asd is an array of immutable(dchar), not imutable(char). At least DMD tells me that its element type is 'dchar'. No, that is not true. It's still an array of immutable(char). The compiler still sees it as an array of immutable(char). However, std.range forces the element type of char[] and wchar[] to be bidirectional ranges of dchar. The tests such as isRandomAccessRange and ElementType are fudged to say string is *not* a random access range, and its element type is dchar. This was one of Andrei's changes because without such shoehorning, std.algorithm could possible start shearing off strings that weren't valid. Whether that was the right decision remains to be seen. I personally would rather have special ranges that do those things. If I have a string that's always in English, why do I need to generate the dchars based on the characters in that array? -Steve
Re: Why doesn't this work in D2?
On 2010-06-28 14:14, Philippe Sigaud wrote:
On Mon, Jun 28, 2010 at 10:56, Jacob Carlborg d...@me.com
mailto:d...@me.com wrote:
Something to keep in mind: as of 2.04x (.045? maybe), the way UTF-8 /
UTF-32 is managed was changed. asd is an array of immutable(dchar),
not imutable(char). At least DMD tells me that its element type is 'dchar'.
So your function can be done this way in D2:
void foo(T,U)(in T[] a, U b) if (is(U : Unqual!T)) // that compiles only
if b can be cast to A
{
writeln(a,b);
}
asd.foo('s'); // prints asds.
is(U == Unqual!T) does not work, for U is 'char' while Unqual!T is 'dchar'.
More generally, using ranges and not arrays, the template becomes a bit
more heavy:
void foo(Range,Elem)(in Range range, Elem elem)
if (isInputRange!Range is(Elem : Unqual!(ElementType!Range)))
{
...
}
I don't think I understand what you're showing here. How would I
strip off the const/immutable with a template ?
Hmmm...
* plays with is expressions *
This seems to work:
template UnConst(T)
{
static if (is(T t == const U, U)) // that is: 'if T is a 'const U',
for some U'
alias U UnConst; // then give me the U,
(ie, T without a const)
else
alias T UnConst; // else give me the
(original) T
}
template UnImmutable(T)
{
static if (is(T t == immutable U, U)) // 'if T is an 'immutable U',
for some U'
alias U UnImmutable;
else
alias T UnImmutable;
}
test:
void main() {
alias const int Int;
writeln(UnConst!Int.stringof);
writeln(Int.stringof);
writeln(UnConst!int.stringof);
writeln(UnConst!(const int).stringof);
writeln(UnConst!(immutable int).stringof);
alias immutable int IInt;
writeln(UnConst!IInt.stringof);
writeln(IInt.stringof);
writeln(UnImmutable!int.stringof);
writeln(UnImmutable!(const int).stringof);
writeln(UnImmutable!(immutable int).stringof);
}
Philippe
Hmm, now I don't know what I'm doing, I thought you could do something
like this:
template Char (T)
{
alias T Char;
}
void foo (T) (Char!(T) b)
{
}
void main ()
{
foo('s');
}
--
/Jacob Carlborg
Re: Why doesn't this work in D2?
Hello Jacob, On 2010-06-28 02:28, BCS wrote: One solution would be to have templates strip off const/immutable from the top level of args. [...] This solution would match the proposal that popped up a while ago to allow value assignment from const/immutable to mutable. I don't think I understand what you're showing here. How would I strip off the const/immutable with a template ? I was proposing a language change Sorry for any confusion. The idea is that unless the user ask for it explicitly, there is no particular reason to preserve const/immutable for the value portion (true value types and the first level of references/pointers) of arguments. -- ... IXOYE
Re: Why doesn't this work in D2?
On Mon, Jun 28, 2010 at 14:35, Steven Schveighoffer schvei...@yahoo.comwrote: On Mon, 28 Jun 2010 08:14:12 -0400, Philippe Sigaud philippe.sig...@gmail.com wrote: On Mon, Jun 28, 2010 at 10:56, Jacob Carlborg d...@me.com wrote: Something to keep in mind: as of 2.04x (.045? maybe), the way UTF-8 / UTF-32 is managed was changed. asd is an array of immutable(dchar), not imutable(char). At least DMD tells me that its element type is 'dchar'. No, that is not true. It's still an array of immutable(char). The compiler still sees it as an array of immutable(char). However, std.range forces the element type of char[] and wchar[] to be bidirectional ranges of dchar. The tests such as isRandomAccessRange and ElementType are fudged to say string is *not* a random access range, and its element type is dchar. This was one of Andrei's changes because without such shoehorning, std.algorithm could possible start shearing off strings that weren't valid. Ah yes, indeed, you're right. Whether that was the right decision remains to be seen. I personally would rather have special ranges that do those things. If I have a string that's always in English, why do I need to generate the dchars based on the characters in that array? All that I can say is that it instantly broke dozens of unit tests in my projects, which were using strings a simple random-access ranges. It took me 2 DMD releases to work my way uout of it. Maybe I should have a look at byCodeUnit or somesuch. But for clueless users like me, strings suddenly became much more complicated to use. Maybe I was using them in unsafe ways, I don't know. I just hope for a way to get my simple strings back.
Re: Why doesn't this work in D2?
On 2010-06-28 15:48, BCS wrote: Hello Jacob, On 2010-06-28 02:28, BCS wrote: One solution would be to have templates strip off const/immutable from the top level of args. [...] This solution would match the proposal that popped up a while ago to allow value assignment from const/immutable to mutable. I don't think I understand what you're showing here. How would I strip off the const/immutable with a template ? I was proposing a language change Sorry for any confusion. The idea is that unless the user ask for it explicitly, there is no particular reason to preserve const/immutable for the value portion (true value types and the first level of references/pointers) of arguments. Ok, now I understand. -- /Jacob Carlborg
Why doesn't this work in D2?
Why doesn't the following code work in D2 (it works in D1)?
void foo (T) (in T[] a, T b)
{
}
void main ()
{
asd.foo('s');
}
The error I get is:
main.d(10): Error: template main.foo(T) does not match any function
template declaration
main.d(10): Error: template main.foo(T) cannot deduce template function
from argument types !()(string,char)
It seems to be some problem with the b argument, if I change that to
char it works.
--
/Jacob Carlborg
Re: Why doesn't this work in D2?
On 06/27/2010 12:18 PM, Jacob Carlborg wrote:
Why doesn't the following code work in D2 (it works in D1)?
void foo (T) (in T[] a, T b)
{
}
void main ()
{
asd.foo('s');
}
asd.foo(cast(immutable) 's');
Re: Why doesn't this work in D2?
Jacob Carlborg d...@me.com wrote:
Why doesn't the following code work in D2 (it works in D1)?
void foo (T) (in T[] a, T b)
{
}
void main ()
{
asd.foo('s');
}
The error I get is:
main.d(10): Error: template main.foo(T) does not match any function
template declaration
main.d(10): Error: template main.foo(T) cannot deduce template function
from argument types !()(string,char)
It seems to be some problem with the b argument, if I change that to
char it works.
In D2, strings are of type immutable(char)[], so your T would be
immutable(char). However, 's' is a simple, unadorned char.
Ways to fix this would include:
void foo(T)(const T[] a, const T b){
...
}
void foo(T,U)(const T[] a, U b) if (is(Unqual!T == Unqual!U)) {
...
}
--
Simen
Re: Why doesn't this work in D2?
On 2010-06-27 19:26, Simen kjaeraas wrote:
Jacob Carlborg d...@me.com wrote:
Why doesn't the following code work in D2 (it works in D1)?
void foo (T) (in T[] a, T b)
{
}
void main ()
{
asd.foo('s');
}
The error I get is:
main.d(10): Error: template main.foo(T) does not match any function
template declaration
main.d(10): Error: template main.foo(T) cannot deduce template
function from argument types !()(string,char)
It seems to be some problem with the b argument, if I change that to
char it works.
In D2, strings are of type immutable(char)[], so your T would be
immutable(char). However, 's' is a simple, unadorned char.
Ways to fix this would include:
void foo(T)(const T[] a, const T b){
...
}
void foo(T,U)(const T[] a, U b) if (is(Unqual!T == Unqual!U)) {
...
}
That's annoying, specially since char is a value type. I would
preferably have a solution for both D1 and D2. Can I use a template to
cast/alias away the immutable part?
--
/Jacob Carlborg
Re: Why doesn't this work in D2?
Hello Jacob,
That's annoying, specially since char is a value type. I would
preferably have a solution for both D1 and D2. Can I use a template to
cast/alias away the immutable part?
One solution would be to have templates strip off const/immutable from the
top level of args.
void F1(T)(T t) { pragam(msg,typeof(t).stringof); }
string s1;
immutable(char[]) s2
char[] s3
F1(s1); // immutable(char)[] // all as normal
F1(s2); // immutable(char)[] // making a mutable copy of a immutable value
is OK
F1(s3); // char[] // all as normal
void F2(T)(immutable T t) { pragam(msg,typeof(t).stringof); }
F2(s1); // immutable(char[]) // making an immutable copy of a mutable reference
to immutable data is ok
F2(s2); // immutable(char[]) // all as normal
F2(s3); // error, invalid conversion
This solution would match the proposal that popped up a while ago to allow
value assignment from const/immutable to mutable.
--
... IXOYE
