# Heuristics
(Mixing Go and Haskell notations...)
从类型 f 指向类型 g，则用 g 的实例可以实现 f 的实例。（考虑 柯里-霍华德对应。）
例：
// func(string) (int, error) -> func(string) int
// 一种实现方式：
func Atoi(s string) (int, error);
func MustAtoi(s string) int {
i, _ := Atoi(s)
return i
}
## Distances:
0.
a -> b <~~> a -> b // identical (ID)
1.
(x1,x2) -> (y1,y2) <~~> (x2,x1) -> (y1,y2) // permute params (PP)
(x1,x2) -> (y1,y2) <~~> (x1,x2) -> (y2,y1) // permute results (PR)
2.
(x1,x2) -> (y1,y2) ~~> (x1,x2) -> y2 // weaken results (WR)
3. // Motivation: query `func(string)int` => get too many `func() int` before the expected `strconv.Atoi :: func(string) (int, error)`
(x1,x2) -> (y1,y2) <~~ x2 -> (y1,y2) // weaken params (WP)
- subtyping
- currying? convenient or trouble?
- a -> b ~~ a -> c // possible first step
- a -> b ~~ c -> b // possible last step
- Fuzzy context: “Type name, type only name” ~~> Guess what user means (module, package, version)
- type (v.)
- according to popularity?
- Beyond expectation:
- `func([]string) []int` ~~> `func[a,b any]([]a) []b`
- `func([]string) []int` ~~> `func[a,b any]([]a, func(a) b) []b` + `func(string) int`
...