How to do nested function declarations (functions inside functions) in Go?

Question

Lambdas work as expected: func main() { inc := func(x int) int { return x+1; } } However, the following declaration inside a declaration is not allowed: func main() { func inc(x int) int { return x+1; } } For what reason are nested functions not allowed?

Chris Gregori · Accepted Answer

Nested functions are allowed in Go. You just need to assign them to local variables within the outer function, and call them using those variables. func outerFunction(iterations int, s1, s2 string) int { someState := 0 innerFunction := func(param string) int { // Could have another nested function here! totalLength := 0 // Note that the iterations parameter is available // in the inner function (closure) for i := 0; i < iterations; i++) { totalLength += len(param) } return totalLength } // Now we can call innerFunction() freely someState = innerFunction(s1) someState += innerFunction(s2) return someState } myVar := outerFunction(100, "blah", "meh")

Go Language

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