関数をpipeにする
- 関数呼び出しのシンタックスは醜い
- Range Library Proposalではoperator|を使った回避策が提案されている
- これはRangeに限った話ではないので、result_ofを使って書こう (実装)
[]#include[] []<boost/utility/result_of.hpp>[]
[]#include[] []<pstade/pipable.hpp>[]
[]int[] []increment[][]([][]int[] []i[][])[]
[]{[]
[]return[] []i[][] + [][]1[][];[]
[]}[][]int[] []decrement[][]([][]int[] []i[][])[]
[]{[]
[]return[] []i[][] - [][]1[][];[]
[]}[][]int[] []multiply[][]([][]int[] []i[][], [][]int[] []j[][])[]
[]{[]
[]return[] []i[][] * [][]j[][];[]
[]}[]
[]using[] []namespace[] []pstade[][];[]
[]typedef[]
[]pipable_fun[]
[]typeof_pipable[][];[]
[]boost[][]::[][]result_of[][]<[][]typeof_pipable[][]([][]int[][] (*)([][]int[][]))>::[][]type[] []incremented[][] =[]
[]pipable[][](&[][]increment[][]);[][]boost[][]::[][]result_of[][]<[][]typeof_pipable[][]([][]int[][] (*)([][]int[][]))>::[][]type[] []decremented[][] =[]
[]pipable[][](&[][]decrement[][]);[][]boost[][]::[][]result_of[][]<[][]typeof_pipable[][]([][]int[][] (*)([][]int[][], [][]int[][]))>::[][]type[] []multiplied[][] =[]
[]pipable[][](&[][]multiply[][]);[]
[]void[] []test[][]()[]
[]{[]
[]BOOST_CHECK[][]( [][]7[][] == [][]decrement[][]([][]multiply[][]([][]increment[][]([][]3[][]), [][]2[][])) );[]
[]BOOST_CHECK[][]( [][]7[][] == ( [][]3[][]|[][]pipable[][](&[][]increment[][])|[][]pipable[][](&[][]multiply[][])([][]2[][])|[][]pipable[][](&[][]decrement[][]) ) );[]
[]BOOST_CHECK[][]( [][]7[][] == ( [][]3[][]|[][]incremented[][]|[][]multiplied[][]([][]2[][])|[][]decremented[][] ) );[]
[]}[]
