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Re: Using enable_if and function templates

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dar...@gmail.com於 2011年12月30日星期五UTC+8上午10時43分45秒寫道：
> Let's say we have a function template like:
> 
> template < typename T, unsigned M, unsigned N >
> int  array_compare( T const (&l)[M], T const (&r)[N] );  // -1, 0 , or +1
> 
> where if the lengths are unequal, consider the missing values of the shorter object as zero.  Can we use enable_if and function template default-parameters to segregate the code for M > N, M == N, and M < N?
> 
> template < typename T, unsigned M, unsigned N, typename DoIt = enable_if<(M > N)>::type >
> int  array_compare( T const (&l)[M], T const (&r)[N] )
> {
>    // compare l[0..N-1] to r[0..N-1]
>    // if result_so_far == 0, return comparing l[N..M-1] positively
> }
> 
> template < typename T, unsigned S >
> int  array_compare( T const (&l)[S], T const (&r)[S] )
> {
>     for ( T const *ll = l, *rr = r ; ll < l + S ; ++ll, ++rr )

The pointer ll won't be overflow.  The length par of S is passed by ????

If S is fixed, this is just trivial in the compiler. 

 




>     {
>         if ( *ll > *rr ) return +1;
>         if ( *ll < *rr ) return -1;
>     }
>     return 0;
> }
> 
> template < typename T, unsigned M, unsigned N, typename DoIt = enable_if<(M < N)>::type >
> int  array_compare( T const (&l)[M], T const (&r)[N] )
> {
>    // compare l[0..M-1] to r[0..M-1]
>    // if result_so_far == 0, return comparing r[M..N-1] negatively
> }
> 
> If this works, can it also work on operator templates?
> 
> Daryle W.

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Using enable_if and function templates darylew@gmail.com - 2011-12-29 18:43 -0800
  Re: Using enable_if and function templates "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2011-12-30 04:14 +0100
  Re: Using enable_if and function templates 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 19:16 -0800

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