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Function currying in Go.
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| package main | |
| import ( | |
| "fmt" | |
| "reflect" | |
| ) | |
| type G interface{} | |
| type F func(...G) G | |
| func (f F) Apply(a G) F { | |
| return func(values ...G) G { | |
| values = append([]G{a}, values...) | |
| return f(values...) | |
| } | |
| } | |
| func Apply(fn G, args ...G) F { | |
| var fun = wrap(fn) | |
| for _, arg := range args { | |
| fun = fun.Apply(arg) | |
| } | |
| return fun | |
| } | |
| func ApplyAll(fn G, args ...G) G { | |
| fnT := reflect.TypeOf(fn) | |
| if fnT.Kind() != reflect.Func { | |
| panic(fmt.Errorf("%T must be a function", fn)) | |
| } | |
| l := len(args) | |
| if fnT.NumIn() > l { | |
| return Apply(fn, args...) | |
| } else | |
| if fnT.NumIn() == l { | |
| return Apply(fn, args...)() | |
| } else { | |
| panic(fmt.Errorf("%v arguments are too many for function %T", l, fn)) | |
| } | |
| } | |
| func wrap(fn G) F { | |
| return func(a ...G) G{ | |
| return invoke(fn, a) | |
| } | |
| } | |
| func invoke(fn G, args []G) G { | |
| var vs []reflect.Value | |
| for _, arg := range args { | |
| vs = append(vs, reflect.ValueOf(arg)) | |
| } | |
| fun := reflect.ValueOf(fn) | |
| return fun.Call(vs)[0].Interface() | |
| } | |
| func Curry(fn G, args []G) F { | |
| var f F = wrap(fn) | |
| for _, elem := range args { | |
| f = f.Apply(elem) | |
| } | |
| return f | |
| } | |
| func sum(a int, b int, c int) int { | |
| return a + b + c | |
| } | |
| func size(a int, b string) int { | |
| return a + len(b) | |
| } | |
| func main() { | |
| fmt.Println(wrap(sum).Apply(1)(2, 3)) //6 | |
| fmt.Println(wrap(sum).Apply(1).Apply(2)(3)) //6 | |
| fmt.Println(wrap(sum).Apply(1).Apply(2).Apply(3)()) //6 | |
| fmt.Println(Apply(sum, 1)(2, 3)) //6 | |
| fmt.Println(Apply(sum, 1, 2)(3)) //6 | |
| fmt.Println(Apply(sum, 1, 2, 3)()) //6 | |
| fmt.Println(ApplyAll(sum, 1, 2, 3)) //6 | |
| fmt.Println(ApplyAll(sum, 1, 2).(F)(3)) //6 | |
| fmt.Println(Apply(Apply(Apply(sum, 3),2),1)()) //6 | |
| fmt.Println(Apply(size, 1)("ab")) //3 | |
| fmt.Println(Apply(size, 1, "ab")()) //3 | |
| fmt.Println(Curry(sum, []G{1})(2, 3)) //6 | |
| fmt.Println(Curry(sum, []G{1, 2})(3)) //6 | |
| fmt.Println(Curry(sum, []G{1, 2, 3})()) //6 | |
| fmt.Println(Curry(size, []G{1})("ab")) //3 | |
| fmt.Println(Curry(size, []G{1, "ab"})()) //3 | |
| } |
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