Re: [Boost-users] template int argument

From: Sakharuk, Vlad \(GMI Development\) (Vlad_Sakharuk_at_[hidden])
Date: 2008-03-25 13:16:06

Compiler does optimize it away. But it should compile it first to
validate correctness of the code.
Btw on "g++ (GCC) 3.4.6 20060404 (Red Hat 3.4.6-3)" I do not see those
warnings.

I also prefer to use:
if(n==2)
if(n==3)//without else.

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of Hicham Mouline
Sent: Tuesday, March 18, 2008 2:56 PM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] template int argument

That's what I thought...

What forbids the compiler from optimizing away the test on n value,
during the template instantiation process?

Thanks,
-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of Steven
Watanabe
Sent: 18 March 2008 18:47
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] template int argument

AMDG

Hicham Mouline wrote:
> hi,
>
> I have a template function <typename cT, typename tT, int n> {
> ....
> double array[n];
>
> if (n==2)
>   binomial code
> else if (n==3)
>   trinomial code  (array[0] array[1] array[2])
> else
> ....
>
>
> compiler tries to compile the "trinomial code" code even when the 
> template

> is instantiated with n=2,
> and that gives warnings because of array[2]
>
> Is there a way to make the compiler ignore the non-binomial code ? 
> rds,

You'll have to split it out into a separate function and use template 
specialization/overload resolution.

template<int n>
void do_n_specific_code(double (&array)[n]);

template<typename cT, typename tT, int n>
void f() {
    double array[n];

    do_n_specific_code(array);

}

In Christ,
Steven Watanabe

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