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May 06, 2005
lost and mixed in
Why doesn't this work:

# template MFoo(T)
# {
# 	T foo(T a)
# 	{
# 		return a;
# 	}
# }
#
# class Foo
# {
# 	mixin MFoo!(int);
# 	mixin MFoo!(int*);
# }
#
# void main()
# {
# 	Foo f = new Foo;
# 	f.foo(2);
# }

Error:
"console_main.d(3): function console_main.Foo.MFoo!(int) MFoo_i.foo 
conflicts with console_main.Foo.MFoo!(int*) MFoo_Pi.foo at 
console_main.d(3)"


On the other hand, this code is just fine:

# class Foo
# {
# 	int foo(int a)
# 	{
# 		return a;
# 	}
#
# 	int* foo(int* a)
# 	{
# 		return a;
# 	}
# }
#
# void main()
# {
# 	Foo f = new Foo;
# 	f.foo(2);
# }


Am I missing/mixing something about mixins ? I'd really like the mixin 
code to work... right now I have to make huge cut'n'pasting in my project :(


-- 
Tomasz Stachowiak  /+ a.k.a. h3r3tic +/
May 06, 2005
Re: lost and mixed in
See if this works:

# class Foo
# {
# 	mixin MFoo!(int) MFooMix1;
#       alias MFooMix.foo foo;
# 	mixin MFoo!(int*) MFooMix2;
#       alias MFooMix.foo foo;
# }
May 06, 2005
Re: lost and mixed in
On Fri, 06 May 2005 19:04:31 +0200, Tom S wrote:

> Why doesn't this work:
> 
> # template MFoo(T)
> # {
> # 	T foo(T a)
> # 	{
> # 		return a;
> # 	}
> # }
> #
> # class Foo
> # {
> # 	mixin MFoo!(int);
> # 	mixin MFoo!(int*);
> # }
> #
> # void main()
> # {
> # 	Foo f = new Foo;
> # 	f.foo(2);
> # }
> 
> Error:
> "console_main.d(3): function console_main.Foo.MFoo!(int) MFoo_i.foo 
> conflicts with console_main.Foo.MFoo!(int*) MFoo_Pi.foo at 
> console_main.d(3)"
> 
> 
> On the other hand, this code is just fine:
> 
> # class Foo
> # {
> # 	int foo(int a)
> # 	{
> # 		return a;
> # 	}
> #
> # 	int* foo(int* a)
> # 	{
> # 		return a;
> # 	}
> # }
> #
> # void main()
> # {
> # 	Foo f = new Foo;
> # 	f.foo(2);
> # }
> 
> 
> Am I missing/mixing something about mixins ? I'd really like the mixin 
> code to work... right now I have to make huge cut'n'pasting in my project :(

If one reads the mixin documents, one gets the impression that it is a
method of inserting code _as if it had been coded in_. However, mixins are
not exactly boilerplate code snippets. Which is a crying shame, if you ask
me. 

Using your example, one could have thought that it was as if you had coded
...

# class Foo
# {
#    int foo(int a)
#    {
#        return a;
#    }
#    int* foo(int* a)
#    {
#        return a;
#    }
#}
#void main()
#{
#    Foo f = new Foo;
#    f.foo(2);
#}

which compiles just fine. But using mixins you have to go over some stupid
looking hurdles.

#template MFoo(T)
#{
#    T foo(T a)
#    {
#        return a;
#    }
#}
#class Foo
#{
#  mixin  MFoo!(int)  mint; alias mint.foo foo;
#  mixin  MFoo!(int*) mintp; alias mintp.foo foo;
#}
#void main()
#{
#    Foo f = new Foo;
#    f.foo(2);
#}

So, to repeat myself, mixins are not macros. 

 mixin MFoo!(int)

does not exactly generate ...

 int foo(int a)
 {
   return a;
 }

as you would naturally expect. Its more like creating a variable
declaration, and having two variables with the same name in the same scope
is a conflict.

I think it is a mistake that one day Walter will see fit to correct.

-- 
Derek Parnell
Melbourne, Australia
http://www.dsource.org/projects/build v2.06 is now available. 04/May/2005
7/05/2005 4:25:35 AM
May 08, 2005
Re: lost and mixed in
Derek Parnell wrote:
> So, to repeat myself, mixins are not macros. 
> 
>   mixin MFoo!(int)
> 
> does not exactly generate ...
> 
>   int foo(int a)
>   {
>     return a;
>   }
> 
> as you would naturally expect. Its more like creating a variable
> declaration, and having two variables with the same name in the same scope
> is a conflict.
> 
> I think it is a mistake that one day Walter will see fit to correct.


Sorry I haven't replied earlier, but only now I could get back to my 
comp for a longer while.
Thank you (and Sean) for helping me out with this issue, but I don't 
quite like the solution... I hope this problem will be fixed / resolved 
in future (or rather: Walter resolves it)
I've gone with another solution, which at least looks better in the 
implementation /* I'd have to define many of these mixin FooMixin1 .. 
FooMixinN as I'm using it for custom classes rather than for int and 
int* ... */ I'm just mixing in a single template which has the desired 
code generated by a python script (like a marco -> shame), lies in a 
separate file/module and at least works exactly as I want it to...


-- 
Tomasz Stachowiak  /+ a.k.a. h3r3tic +/
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