I just thought I'd give D another try, after having given up on it for a while.

Lo and behold... the same old kind of problem from a year ago is still here. :(

Simple stuff like this:

    import std.algorithm;
    void main() {
        const arr = [1, 2, 3];
        reduce!"a*b"(arr);   // You'd think it'd work...
    }

Results in ridiculously annoying errors like:
    // algorithm.d(728): Error: can only initialize const member _field_field_0 inside constructor

I **HIGHLY** suggest that priority be given to simple problems like these, instead of OMG-so-cool-libraries. It really doesn't matter if there is an uber-awesome collections/CURL/whatever library out there, when problems like these exist. If a 2-line piece of code needs a workaround, then (IMO) people simply won't care about anything else that's more complicated.

I'll post more as I find them. (I'd found plenty a few months ago, now I just need to find them again.)
Too lazy/busy studying to post as a bug. And it feels a bit better when I add the complaint. :P

(Sorry for being so critical but at least I tried to make it constructive...)

Moar coming... hey look, it's ANOTHER const-ness issue! :(

import std.algorithm;
struct Matrix
{
    size_t[] _lengths;
    @property inout(size_t)[] lengths() inout { return _lengths; }
    @property size_t length() inout { return reduce!q{a*b}(lengths); }
}

// Error: template std.algorithm.reduce!("a*b").reduce(Args...) if (Args.length > 0 && Args.length <= 2 && isIterable!(Args[__dollar - 1])) does not match any function template declaration
// Error: template std.algorithm.reduce!("a*b").reduce(Args...) if (Args.length > 0 && Args.length <= 2 && isIterable!(Args[__dollar - 1])) cannot deduce template function from argument types !()(inout(uint[2u]))

On 12/10/2011 10:43 AM, Mehrdad wrote:
> Moar coming... hey look, it's ANOTHER const-ness issue! :(
>
> import std.algorithm;
> struct Matrix
> {
> size_t[] _lengths;
> @property inout(size_t)[] lengths() inout { return _lengths; }
> @property size_t length() inout { return reduce!q{a*b}(lengths); }
> }
>
> // Error: template std.algorithm.reduce!("a*b").reduce(Args...) if
> (Args.length > 0 && Args.length <= 2 && isIterable!(Args[__dollar - 1]))
> does not match any function template declaration
> // Error: template std.algorithm.reduce!("a*b").reduce(Args...) if
> (Args.length > 0 && Args.length <= 2 && isIterable!(Args[__dollar - 1]))
> cannot deduce template function from argument types !()(inout(uint[2u]))

http://d.puremagic.com/issues/show_bug.cgi?id=6809

On 12/10/2011 10:37 AM, Mehrdad wrote:
> I just thought I'd give D another try, after having given up on it for a
> while.
>
> Lo and behold... the same old kind of problem from a year ago is still
> here. :(
>
> Simple stuff like this:
>
> import std.algorithm;
> void main() {
> const arr = [1, 2, 3];
> reduce!"a*b"(arr); // You'd think it'd work...
> }
>
> Results in ridiculously annoying errors like:
> // algorithm.d(728): Error: can only initialize const member
> _field_field_0 inside constructor
>
> I **HIGHLY** suggest that priority be given to simple problems like
> these, instead of OMG-so-cool-libraries.

It is a *library bug*. Just have a look at the source code.

> It really doesn't matter if
> there is an uber-awesome collections/CURL/whatever library out there,
> when problems like these exist. If a 2-line piece of code needs a
> workaround, then (IMO) people simply won't care about anything else
> that's more complicated.
>
> I'll post more as I find them. (I'd found plenty a few months ago, now I
> just need to find them again.)
> Too lazy/busy studying to post as a bug. And it feels a bit better when
> I add the complaint. :P
>
> (Sorry for being so critical but at least I tried to make it
> constructive...)

Just slice the const array to get a range. The specialization for ranges does not have the bug.

import std.algorithm;
void main() {
    const arr = [1, 2, 3];
    reduce!"a*b"(arr[]);   // It works.
}

... and another...

struct S(T, int N)
{ public auto opBinary(string op)(in S!(T, N) other) const { return this; } }
void main() { S!(int, 1) m; m = m * m; }

Error: 'm' is not of arithmetic type, it is a Matrix!(int,1)
Error: 'm' is not of arithmetic type, it is a Matrix!(int,1)

On Sat, 10 Dec 2011 12:18:31 +0200, Mehrdad <wfunction@hotmail.com> wrote:

> ... and another...
>
> struct S(T, int N)
> { public auto opBinary(string op)(in S!(T, N) other) const { return this; } }
> void main() { S!(int, 1) m; m = m * m; }
>
> Error: 'm' is not of arithmetic type, it is a Matrix!(int,1)
> Error: 'm' is not of arithmetic type, it is a Matrix!(int,1)

Oh fantastic, so you are writing the first bug-free software of our time?

On 12/10/2011 2:28 AM, so wrote:
> On Sat, 10 Dec 2011 12:18:31 +0200, Mehrdad <wfunction@hotmail.com> wrote:
>
>> ... and another...
>>
>> struct S(T, int N)
>> { public auto opBinary(string op)(in S!(T, N) other) const { return this; } }
>> void main() { S!(int, 1) m; m = m * m; }
>>
>> Error: 'm' is not of arithmetic type, it is a Matrix!(int,1)
>> Error: 'm' is not of arithmetic type, it is a Matrix!(int,1)
>
> Oh fantastic, so you are writing the first bug-free software of our time?

Nope, sorry. :(
I'm listing a bunch of bugs I've found. And yes, I'm [semi-]complaining about them in the process.

... and another...

struct Matrix(T, size_t N = 1)
{ public auto mul(Matrix!(T, N) other) const { return this; } }

void main()
{
    Matrix!(int, 2) m;
    m.mul(m);
}

annoy.d(7): Error: function annoy.Matrix!(int,2).Matrix.mul (Matrix!(int,N) other) const is not callable using argument types (Matrix!(int,2))
annoy.d(7): Error: cannot implicitly convert expression (m) of type Matrix!(int,2) to Matrix!(int,N)

... and another...

struct S(L...) {
    enum N = L[0];
    S!(N) me() { return this; }
}
alias S!(1) S2;

annoy.d(3): Error: template instance annoy.S!(N) recursive expansion

Timon Gehr:

> Just slice the const array to get a range. The specialization for ranges does not have the bug.
> 
> import std.algorithm;
> void main() {
>      const arr = [1, 2, 3];
>      reduce!"a*b"(arr[]);   // It works.
> }

Wasn't arr a range already?

Bye,
bearophile