Re: Math Functions: pow and type promotion

From: Eric Ford (eford_at_[hidden])
Date: 2001-10-09 15:28:29

> There is documentation:  std_math.html

I haven't looked at the code, but the documentation looks good.
Thanks for doing that.  

Am I correct that the next step is to try to persuade people to
provide patches or at least feedback so it can become portable?

I don't understand the pow issue.
What's wrong with something like type promotion often used for the
arithmetic operators?

// tag to indicate power operation
struct pow_tag {};

// declaration of general type promotion class
template< typename Arg1T, typename Arg2T, typename OpT >
struct promote_type;  

// specializations for pow
template<typename T> struct promot_type<T,T,pow_tag> { typedef T
return_type; };
template<> struct promot_type<int,float,pow_tag> { typedef float
return_type; };
template<> struct promot_type<float,int,pow_tag> { typedef float
return_type; };
// ...

template<typename BaseT, typename PowerT>
typename promote_type<BaseT,PowerT,pow_tag>::return_type 
pow(BaseT x, PowerT a);

BTW- It might be nice if we used a general type promotion framework. 
Is someone working on that?  If so, what's the status?  Is there a
working version we could use?  If not, we could modify the
unit_promotion code I posted in qualified_unit.

E