Re: new __builtin_choose_type (patch)

[Aldy Hernandez <aldyh at redhat dot com>]

On Tue, 2001-10-02 at 15:04, Joseph S. Myers wrote:
> On 2 Oct 2001, Aldy Hernandez wrote:
> 
> > it was suggested to have a builtin analogous to the ?: operator that
> > will work as follows:
> > 
> > 	__builtin_choose_type (exp0, type, exp1, exp2);
> > 
> > if <exp0> is of type <type>, evaluate <exp1> else evaluate <exp2>.
> > 
> > i have a patch for this feature and i'd like some comments.
> 
> Since your patch doesn't add documentation or testcases, I don't know what
> it really intends.  In a case like this, the documentation and the

well i didn't add documentation or testcases because i didn't want to
code the entire thing, docs and all, and have everyone say-- "oh, that's
not the right approach".  that's what i posted info on what i wanted to
do.

example:

    int b;
    double a;
    float float_type;
    
    foo(){  
            __builtin_choose_type(a, float_type, b=8, b=10);
    }
    
in this case, b=10 is evaluated because the type of "a" (double) is not
the type of "float_type" (float).  the value of the entire
builtin_choose_type instruction is 10.

so, in pseudo code:

  typeof(a) == typeof(float_type) ? b=8 : b=10

b=8 is not evaluated at all.

-- 
Aldy Hernandez					E-mail: aldyh@redhat.com
Professional Gypsy on a Motorcycle
Red Hat, Inc.