• bearophile (16/16) May 16 2010 Do you know if it's possible to replace typeof(f1) with f1.typeof in...
• Robert Clipsham (28/44) May 16 2010 The closest I've managed with my quick attempt is:
• bearophile (5/19) May 17 2010 You are right, thank you. At the moment it's a size_t, that is an unsign...

bearophile <bearophileHUGS lycos.com> writes:

Do you know if it's possible to replace  typeof(f1)  with  f1.typeof  in D (for
symmetry with sizeof too)?

import std.stdio: writeln;
struct Foo {
    int x;
}
void main() {
    Foo f1;
    int fsize = f1.sizeof; // OK
    alias typeof(f1) T1;   // OK
    alias f1.typeof T2;    // ERR
}


[What I'd like is this, but this is for another thread:
Type T2 = f1.typeof;
]

Bye,
bearophile

Robert Clipsham <robert octarineparrot.com> writes:

On 16/05/10 21:43, bearophile wrote:
 Do you know if it's possible to replace  typeof(f1)  with  f1.typeof  in D
(for symmetry with sizeof too)?

 import std.stdio: writeln;
 struct Foo {
      int x;
 }
 void main() {
      Foo f1;
      int fsize = f1.sizeof; // OK
      alias typeof(f1) T1;   // OK
      alias f1.typeof T2;    // ERR
 }


 [What I'd like is this, but this is for another thread:
 Type T2 = f1.typeof;
 ]

 Bye,
 bearophile

The closest I've managed with my quick attempt is:
----
mixin template typeOf()
{
	alias typeof(this) typeOf;
}
struct Foo
{
	int x;
	mixin typeOf;
}
void main() {
     Foo f1;
     auto fsize = f1.sizeof; // OK
     alias typeof(f1) T1;   // OK
     alias f1.typeOf T2;    // OK
}
----

It's not ideal, but it works. You can choose a capitalization to suit 
you. If you want the capitalization to match you can make a similar 
template for sizeof to keep things consistent.

A couple of other things to note, I changed fsize to auto, as the type 
of .sizeof is different on x86_64, this isn't an issue now, but it's 
nice to keep code portable! Another thing is template bloat - I haven't 
looked properly, it seems that the template is optimized out though, so 
using it doesn't add any overhead... I could be wrong though.

Robert

bearophile <bearophileHUGS lycos.com> writes:

Robert Clipsham:

 The closest I've managed with my quick attempt is:
 ----
 mixin template typeOf()
 {
 	alias typeof(this) typeOf;
 }
 struct Foo
 {
 	int x;
 	mixin typeOf;
 }

Thank you for your code :-) Your example shows this feature can become a
built-in.


 I changed fsize to auto, as the type 
 of .sizeof is different on x86_64, this isn't an issue now, but it's 
 nice to keep code portable!

You are right, thank you. At the moment it's a size_t, that is an unsigned CPU
word. (I have recently asked in bugzilla for all those values to become signed
words, because unsigned are too much unsafe in a language that doesn't catch
signed-unsigned conversions and has no integral overflows tests).

Bye,
bearophile