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package fun
import (
"reflect"
"github.com/BurntSushi/ty"
)
// Memo has a parametric type:
//
// func Memo(f func(A) B) func(A) B
//
// Memo memoizes any function of a single argument that returns a single value.
// The type `A` must be a Go type for which the comparison operators `==` and
// `!=` are fully defined (this rules out functions, maps and slices).
func Memo(f interface{}) interface{} {
chk := ty.Check(
new(func(func(ty.A) ty.B)),
f)
vf := chk.Args[0]
saved := make(map[interface{}]reflect.Value)
memo := func(in []reflect.Value) []reflect.Value {
val := in[0].Interface()
ret, ok := saved[val]
if ok {
return []reflect.Value{ret}
}
ret = call1(vf, in[0])
saved[val] = ret
return []reflect.Value{ret}
}
return reflect.MakeFunc(vf.Type(), memo).Interface()
}