Matafunctionのカスタマイズにenable_ifが使えた

• タグディスパッチはいらなくなった、かもしれない・・・参照

[]#include[] []<string>[]

[]#include[] []<boost/lexical_cast.hpp>[]

[]#include[] []<boost/type_traits/is_base_of.hpp>[]

[]#include[] []<boost/utility/enable_if.hpp>[]

[]struct[] []A[]

[]{[]

    []typedef[] []char[] []char_type[][];[]

[]};[]
[]struct[] []B[][] : [][]A[]

[]{[]

    []char[] []get_string[][]()[]

[]    {[]

        []return[] []'B'[][];[]

[]    }[]

[]};[]
[]struct[] []C[][] : [][]A[]

[]{[]

    []char[] []get_string[][]()[]

[]    {[]

        []return[] []'C'[][];[]

[]    }[]

[]};[]


[]template[][]< [][]class[] []T[][] >[]

[]struct[] []which[][] :[]

    []boost[][]::[][]enable_if[][]<[][]T[][]>[]

[]{ };[]


[]template[][]< [][]class[] []T[][], [][]class[][] = [][]void[][] >[]

[]struct[] []customization[][];[]


[]template[][]< >[]

[]struct[] []customization[][]<[][]int[][]>[]

[]{[]

    []template[][]< [][]class[] []Int[][] >[]

    []struct[] []foo_result[]

[]    {[]

        []typedef[] []std[][]::[][]string[] []type[][];[]

[]    };[]
    []template[][]< [][]class[] []Result[][] >[]

    []Result[] []foo[][]([][]int[] []i[][])[]

[]    {[]

        []return[] []boost[][]::[][]lexical_cast[][]<[][]Result[][]>([][]i[][]);[]

[]    }[]

[]};[]


[]template[][]< [][]class[] []T[][] >[]

[]struct[] []customization[][]<[][]T[][], [][]typename[] []which[][]< [][]boost[][]::[][]is_base_of[][]< ::[][]A[][], [][]T[][] > >::[][]type[][]>[]

[]{[]

    []template[][]< [][]class[] []A_[][] >[]

    []struct[] []foo_result[]

[]    {[]

        []typedef[] []typename[] []A_[][]::[][]char_type[] []type[][];[]

[]    };[]
    []template[][]< [][]class[] []Result[][], [][]class[] []A_[][] >[]

    []Result[] []foo[][]([][]A_[][]& [][]a[][])[]

[]    {[]

        []return[] []a[][].[][]get_string[][]();[]

[]    }[]

[]};[]


[]template[][]< [][]class[] []T[][] >[]

[]typename[][] ::[][]customization[][]<[][]T[][]>::[][]template[] []foo_result[][]<[][]T[][]>::[][]type[]

[]foo[][]([][]T[][]& [][]x[][])[]

[]{[]

    []typedef[] []typename[][] ::[][]customization[][]<[][]T[][]>::[][]template[] []foo_result[][]<[][]T[][]>::[][]type[] []result_t[][];[]

    []return[][] ::[][]customization[][]<[][]T[][]>().[][]template[] []foo[][]<[][]result_t[][]>([][]x[][]);[]

[]}[]


[]void[] []test[][]()[]

[]{[]

    []int[] []i[][] = [][]30[][];[]

    []BOOST_CHECK[][]( ::[][]foo[][]([][]i[][]) == [][]"30"[][] );[]
[]    ::[][]B[] []b[][];[]

[]    ::[][]C[] []c[][];[]

    []BOOST_CHECK[][]( ::[][]foo[][]([][]b[][]) == [][]'B'[][] );[]

    []BOOST_CHECK[][]( ::[][]foo[][]([][]c[][]) == [][]'C'[][] );[]

[]}[]