Hi,

I just learn about auto ref functions and tried this :

import std.stdio;

auto ref foo(int i, ref float f)
{
         if (i < f)
         {
             return i;
         }
         else
         {
             return f;
         }
}

void main()
{
         int i = 1;
         float f1 = 1.1;
         float f2 = 0.9;
         writeln(foo(i, f1));
         writeln(foo(i, f2));
}

Tricky questions : Does it compiles ? If yes what does it do ?
Then my question : How is this possible ?

(you can remove the ref stuff)

Ok this explain it : http://dlang.org/function.html#auto-functions. It should return a float.

In fact I am now thinking it's great...I tried with string instead of float and got a clear error message. I should have read the spec more thoroughly.

On 4/11/15 6:08 AM, matovitch wrote:
> Hi,
>
> I just learn about auto ref functions and tried this :
>
> import std.stdio;
>
> auto ref foo(int i, ref float f)
> {
>           if (i < f)
>           {
>               return i;
>           }
>           else
>           {
>               return f;
>           }
> }
>
> void main()
> {
>           int i = 1;
>           float f1 = 1.1;
>           float f2 = 0.9;
>           writeln(foo(i, f1));
>           writeln(foo(i, f2));
> }
>
> Tricky questions : Does it compiles ? If yes what does it do ?
> Then my question : How is this possible ?

D has great compile-time tools to examine what the compiler is doing.

A great feature of D for investigating compiler internals is pragma(msg, ...). This prints at compile time some message (a string) that is based on the state at the time. For example:

void main()
{
         int i = 1;
         float f1 = 1.1;
         float f2 = 0.9;
         pragma(msg, typeof(foo(i, f1)).stringof); // prints what type foo returns
         auto x = foo(i, f2);
         pragma(msg, typeof(x).stringof); // same thing, but easier to understand.
}

result (prints while compiling):

float
float

-Steve

Thanks for the tip ! I was looking at something like this.

On 04/13/2015 07:44 AM, matovitch wrote:
> Thanks for the tip ! I was looking at something like this.

pragma(msg) has been added to "Programming in D" but it is not available online yet:


https://bitbucket.org/acehreli/ddili/src/ae49747a850fabc3a3e66dcdb3626a991c53632e/src/ders/d.en/templates.d?at=master#cl-696

Ali

On 04/15/2015 10:50 AM, Ali Çehreli wrote:

> pragma(msg) has been added to "Programming in D" but it is not available
> online yet:


Sorry for the spam :( but apparently it is already online:

  http://ddili.org/ders/d.en/templates.html#ix_templates.pragma

Ali