Blog / Go Language Spec

Proxying return values

August 1, 2024

We already saw the “normal” way to return values from functions… But did you know there’s a shortcut if you ever want to directly return the values returned from another function?

Return statements

…

  1. The expression list in the “return” statement may be a single call to a multi-valued function. The effect is as if each value returned from that function were assigned to a temporary variable with the type of the respective value, followed by a “return” statement listing these variables, at which point the rules of the previous case apply.
func complexF2() (re float64, im float64) {
	return complexF1()
}

I use this pretty frequently.

However, note that you cannot mix this with other return values. To demonstrate what I mean, here’s an example that’s not valid.

func foo() (string, string) { /* ... */ }

func bar() (string, string, error) {
	/* some logic */
	return foo(), nil
}

The shortcut only works when the multi-valued function is the only thing being returned. So in this example, we need to use our own explicit temporary variables:

	a, b := foo()
	return a, b, nil

Quotes from The Go Programming Language Specification Language version go1.22 (Feb 6, 2024)

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Return statements, conclusion

Just a couple small notes before we move on from return statements… Return statements … Regardless of how they are declared, all the result values are initialized to the zero values for their type upon entry to the function. A “return” statement that specifies results sets the result parameters before any deferred functions are executed. For the most part, this can be considered trivia, for Quiz night at your next Go meetup.

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Three ways to return values

Return statements … There are three ways to return values from a function with a result type: Do you know all three off the top of your head? We’ll be looking at each of them over the coming three days. The return value or values may be explicitly listed in the “return” statement. Each expression must be single-valued and assignable to the corresponding element of the function’s result type. func simpleF() int { return 2 } func complexF1() (re float64, im float64) { return -7.

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