what the problem with this?

alias myint = mixin("int"); // <- basic type expected blah blah blah...

mixin alias unusable now, it blocks various cool templates and really frustrating(such things make D feels like some cheap limited language), is there any way to tell compiler explicitly use mixin result for aliasing like above?

On Sun, 31 Aug 2014 11:26:47 +0000
evilrat via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

> alias myint = mixin("int"); // <- basic type expected blah blah
  mixin("alias myint = "~"int"~";");
?

On Sunday, 31 August 2014 at 11:43:03 UTC, ketmar via Digitalmars-d-learn wrote:
> On Sun, 31 Aug 2014 11:26:47 +0000
> evilrat via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
> wrote:
>
>> alias myint = mixin("int"); // <- basic type expected blah blah
>   mixin("alias myint = "~"int"~";");
> ?

wow, it works. i don't even think inverting it O_o
you saved my day, thanks.

On Sunday, 31 August 2014 at 12:01:43 UTC, evilrat wrote:
> On Sunday, 31 August 2014 at 11:43:03 UTC, ketmar via Digitalmars-d-learn wrote:
>> On Sun, 31 Aug 2014 11:26:47 +0000
>> evilrat via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
>> wrote:
>>
>>> alias myint = mixin("int"); // <- basic type expected blah blah
>>  mixin("alias myint = "~"int"~";");
>> ?
>
> wow, it works. i don't even think inverting it O_o
> you saved my day, thanks.

It is basically just an annoying grammar limitation that does not allow to use mixin / __traits as an identifier.

> It is basically just an annoying grammar limitation that does not allow to use mixin / __traits as an identifier.

The usual helper template:

```
    alias helper(alias a) = a;
```

helps for aliasing __traits and anonymous function templates (x => x+1), but I don't see an easy solution for mixin inside the current language, apart from pushing the mixin outside.

On Sunday, 31 August 2014 at 14:46:00 UTC, Philippe Sigaud via Digitalmars-d-learn wrote:
>> It is basically just an annoying grammar limitation that does not allow to
>> use mixin / __traits as an identifier.
>
> The usual helper template:
>
> ```
>     alias helper(alias a) = a;
> ```
>
> helps for aliasing __traits and anonymous function templates (x =>
> x+1), but I don't see an easy solution for mixin inside the current
> language, apart from pushing the mixin outside.

I recommend slightly more generic form:

template Alias(T...)
    if (T.length == 1)
{
    alias Alias = T[0];
}

it is quite helpful in templated code to be able to alias _anything_

But yeah, no fun for mixins :(

> I recommend slightly more generic form:
>
> template Alias(T...)
>     if (T.length == 1)
> {
>     alias Alias = T[0];
> }
>
> it is quite helpful in templated code to be able to alias _anything_

That's what I use also, but didn't want another thread on the (T...)
if (T.length ==1) trick :)


>
> But yeah, no fun for mixins :(

Mainly, I slap them in my code, then slowly migrate them outwards (in 'head' position) until that compiles...

On Sunday, 31 August 2014 at 12:01:43 UTC, evilrat wrote:
> On Sunday, 31 August 2014 at 11:43:03 UTC, ketmar via Digitalmars-d-learn wrote:
>> On Sun, 31 Aug 2014 11:26:47 +0000
>> evilrat via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
>> wrote:
>>
>>> alias myint = mixin("int"); // <- basic type expected blah blah
>>  mixin("alias myint = "~"int"~";");
>> ?
>
> wow, it works. i don't even think inverting it O_o
> you saved my day, thanks.

ugh... somewhat related to original problem, made simple template for quick check if type present or provide alternative.

now that is something i am not understand.

sorry for my stupidness :(

--- code
struct A {}
alias coolStruct = typeByName!("MyStruct", A);

// oops, looks like alias is set to template itself, though
// code completion(mono-d) shows it is correctly aliased to A
//
// error: template instance is used as a type
void doSomething(coolStruct cs)
{
 .. do something with struct ..
}

--- template itself
template typeByName(alias Name, Replace)
{
 static if ( __traits(compiles, (mixin(Name~`.sizeof`))) )
  mixin(`alias typeByName = ` ~ Name ~ `;`);
 else
  static if ( (is(Replace == class) || is(Replace == struct)) )
   alias typeByName = Replace;
}

On Mon, 01 Sep 2014 10:57:41 +0000
evilrat via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

here's some more ugly hackery for you:

    string makeAlias(string aliasName, string Name, alias Replace) ()
    {
      static if ( __traits(compiles, (mixin(Name~`.sizeof`))) )
        return `alias `~aliasName~` = ` ~ Name ~ `;`;
      static if ( (is(Replace == class) || is(Replace == struct)) )
        return `alias `~aliasName~` = ` ~ Replace.stringof ~ `;`;
      assert(0);
    }


    struct A {}
    mixin(makeAlias!("coolStruct", "MyStruct", A));

or:

    mixin template makeAlias(string aliasName, string Name, alias Replace)
    {
      static if ( __traits(compiles, (mixin(Name~`.sizeof`))) )
        mixin(`alias `~aliasName~` = ` ~ Name ~ `;`);
      static if ( (is(Replace == class) || is(Replace == struct)) )
        mixin(`alias `~aliasName~` = ` ~ Replace.stringof ~ `;`);
      else static assert(0);
    }


    struct A {}
    mixin makeAlias!("coolStruct", "MyStruct", A);

On Mon, 01 Sep 2014 10:57:41 +0000
evilrat via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

and to check that ugly hackery:

    mixin template makeAlias(string aliasName, string Name, alias
    Replace) {
      static if ( __traits(compiles, (mixin(Name~`.sizeof`))) )
        mixin(`alias `~aliasName~` = ` ~ Name ~ `;`);
      static if ( (is(Replace == class) || is(Replace == struct)) )
        mixin(`alias `~aliasName~` = ` ~ Replace.stringof ~ `;`);
      else static assert(0);
    }


    struct A {}
    struct B {}
    struct C {}
    mixin makeAlias!("coolStruct", "MyStruct", A);
    mixin makeAlias!("coolStruct1", "B", C);

    void doSomething(coolStruct cs)
    {
      static if (!is(typeof(cs) == A)) static assert(0);
      //.. do something with struct ..
    }

    void doSomething1(coolStruct1 cs)
    {
      static if (!is(typeof(cs) == B)) static assert(0);
      //.. do something with struct ..
    }