没有括号的Golang函数调用

Question

I am going through the Golang tutorials on their website and am confused by code similar to this that I've simplified and reproduced here:

package main

import (
    "fmt"
    "math"
)

func main() {
    a := math.Sqrt2
    fmt.Println(a)
}

This prints 1.4142135623730951 in the sandbox. Replacing a := math.Sqrt2 with a := math.Sqrt(2) does the same thing but I'm confused how the function can be called without parentheses. math.Sqrt is not a function pointer here (there is no math.Sqrt2 function anyway, it's a function being passed without any parentheses. The function in the Go documentation here is listed as: func Sqrt(x float64) float64 i.e. with the parameter. So how does that work? Is it just because math.Sqrt() is a simplistic function that Go can assume it's a float64 without the parentheses passed? Am I missing something?

If it helps, I found this phenomenon here in the tutorials on line 14, originally. If anyone could explain this feature to me, that would be awesome. I'd love to learn about it.

Answer 1

There is nothing special happening here. math.Sqrt2 is a constant. You can find the other constants in the math package in the docs.

In general, go doesn't really have any "magic". So if something feels a bit magical, its more than likely just a misunderstanding.