Go Language function value transfer and closure

Function Value Pass

A function is also a value. They can be passed like other values, for example, the function value can be used as a function parameter or a return value.

Package main

Import (
	"FMT"
	"math"
)

func Compute (fn func (float64, float64) float64) float64 { Return
	FN (3, 4)
}

Func Main () {
	Hypot: = Func (x, y float64) float64 {return
		math. SQRT (x*x + y*y)
	}
	fmt. Println (Hypot (5))   //Call hypot function, output

	FMT. Println (Hypot)  //Compute the Hypot function as a parameter to the COMPUTE function, using 3,4 as a parameter call to the Hypot function, the result is 5
	FMT. PRINTLN (COMPUTE) (math. Pow))  //Will math. The POW function acts as an argument to the compute function, using 3,4 as the calling math. Pow function parameter call, the result is Bayi
}

Closure of functions

Package main

Import "FMT"
func adder (i int) func (int) int {
	sum: = I return
	func (x int) int {
		sum = x return
		sum
	}
}

Func adder2 (i int) func () int {
	sum: = I return
	func () int {return
		sum
	}
}

func main () {
  fmt. Printf ("%t\n", Adder2 (3))  //The type returned here is a function func () int
	FMT. Println (Adder2 (3) ())       //Use this method to return to the final result 3
	
	pos, neg: = Adder (1), adder (1) for
	I: = 0; i < 3; i++ {
		FMT.P Rintln (
			pos (i),
			neg ( -2*i),             //This is also the way the closure function is invoked, resulting in 1 1,2-1,4-5
		)
	}