go-generics-tilde

~Type in Go

tags: learning go programming

content

Note

~ is for generics and type constraints
(aka, make the connection: whenever ~ is involved, it’s in the context of generics and type constraints)

• imagine we have:
  • a type constraint Number
  • a named type MyInt
  • a generic function GetInt

// ~ is in the context of generics and type constraint!
// so let's define a type constraint:
type Number interface {
	int64 | float64
}
type MyInt int64
func GetInt[T Number](num T) int {
	return int(num)
}

• we wanna pass MyInt into GetInt:

myInt := MyInt(1)
normalInt := GetInt(MyInt)

• this won't work!

  • because type MyInt is NOT int64 or float64

• but the underlying type of MyInt IS actually int64 tho!

• that’s when we have:

type Number interface {
	~int64 | ~float64
}
// same code as above
normalInt := GetInt(myInt)

• now this works!
• ~int64 means: “any type whose underlying type is int64”

---

• this works too!
• the essence of ~ is that it’s used on type constraint

func GetInt[T ~int64 | ~float64](num T) {
	// some code
}

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• go-generics
• go-type-constraint

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