Hi!

I've got this idea:

' import std.stdio;
'
' debug
' {
'     void trace(char[] T)()
'     {
'         scope (failure) writefln("Trace: ", T);
'     }
' }
' else
' {
'     void trace(char[] T)()
'     {
'     }
' }
'
' float foo(float x, float y)
' {
'     mixin trace!("foo");
'     return x / y;
' }
'
' void bar()
' {
'     writefln("result: ", foo(0., 0.));
' }

As far as I understand it, the "scope (failure) ..." would be mixed into foo's scope, so as soon as foo throws, the trace message should be displayed.

' mixin trace!("msg");

is much nicer than

' debug scope (failure) writefln("msg");

Oh, and congrats on 1.0! :)
Hope D gets picked up by lots of people now!

-mike

-- 
Erstellt mit Operas revolutionärem E-Mail-Modul: http://www.opera.com/mail/

mike wrote:
> Hi!
> 
> I've got this idea:
> 
> ' import std.stdio;
> '
> ' debug
> ' {
> '     void trace(char[] T)()
> '     {
> '         scope (failure) writefln("Trace: ", T);
> '     }
> ' }
> ' else
> ' {
> '     void trace(char[] T)()
> '     {
> '     }
> ' }
> '
> ' float foo(float x, float y)
> ' {
> '     mixin trace!("foo");
> '     return x / y;
> ' }
> '
> ' void bar()
> ' {
> '     writefln("result: ", foo(0., 0.));
> ' }
> 
> As far as I understand it, the "scope (failure) ..." would be mixed into  foo's scope, so as soon as foo throws, the trace message should be  displayed.
> 
> ' mixin trace!("msg");
> 
> is much nicer than
> 
> ' debug scope (failure) writefln("msg");
> 
> Oh, and congrats on 1.0! :)
> Hope D gets picked up by lots of people now!
> 
> -mike
> 

Mixins are for mixing-in declarations, not statements. What you're doing is this:

float foo(float x, float y) {
    mixin trace!("foo");
    return x / y;
}

Becomes:

float foo(float x, float y) {
    void trace() {
        scope (failure) writefln("Trace: ", "foo");
    }
    return x / y;
}

See? The "scope (failure)" is inside a nested function. It applies to the scope of that function, and doesn't help one iota. :-)

-- 
Kirk McDonald
Pyd: Wrapping Python with D
http://pyd.dsource.org

Am 04.01.2007, 00:27 Uhr, schrieb Kirk McDonald <kirklin.mcdonald@gmail.com>:

> Mixins are for mixing-in declarations, not statements. What you're doing is this:
>
> float foo(float x, float y) {
>      mixin trace!("foo");
>      return x / y;
> }
>
> Becomes:
>
> float foo(float x, float y) {
>      void trace() {
>          scope (failure) writefln("Trace: ", "foo");
>      }
>      return x / y;
> }
>
> See? The "scope (failure)" is inside a nested function. It applies to the scope of that function, and doesn't help one iota. :-)

Ow! I see. So no way to do that?

-mike

-- 
Erstellt mit Operas revolutionärem E-Mail-Modul: http://www.opera.com/mail/

mike wrote:
> Am 04.01.2007, 00:27 Uhr, schrieb Kirk McDonald  <kirklin.mcdonald@gmail.com>:
> 
>> Mixins are for mixing-in declarations, not statements. What you're doing  is this:
>>
>> float foo(float x, float y) {
>>      mixin trace!("foo");
>>      return x / y;
>> }
>>
>> Becomes:
>>
>> float foo(float x, float y) {
>>      void trace() {
>>          scope (failure) writefln("Trace: ", "foo");
>>      }
>>      return x / y;
>> }
>>
>> See? The "scope (failure)" is inside a nested function. It applies to  the scope of that function, and doesn't help one iota. :-)
> 
> 
> Ow! I see. So no way to do that?
> 
> -mike
> 

Since you can't mixin statements, not directly.  Any way you do it, you would end up using a function at some point, so you may as well just do that, and rely on the compiler to inline the function for you.

*Actually reads code*

Ooooh, I see what you're up to.  Hmm... that is a tricky one.  You could try using a templated function with a delegate parameter... I have no idea if this actually works; perhaps a template guru could help you with the details :P

> auto trace(T_Return)(char[] name, T_Return delegate() dg)
> {
>     debug scope(failure) writefln("Trace: %s", name);
>     return dg();
> }
>
> float foo(float x, float y)
> {
>     return trace!(float)("foo",
>     {
>         return x / y;
>     });
> }

NB: You might be able to remove the "!(float)" bit, I'm not sure.  I haven't really delved into the newer template stuff...

	-- Daniel