在Go中记录多个返回值

Question

Is there an idiomatic way to log result of a function returning multiple values? This won't compile:

import "log"
func returnPair() (int,int) {
    return 42, 24
}
func main() {
    log.Printf("Returned %v", returnPair())
}

prog.go:7: multiple-value returnPair() in single-value context

UPD summary (special thanks to @rvignacio):

This is a peculiarity in Go syntax:

func eat(args ...interface{}) {}

func eatWithSpice(spice string, args ...interface{}) {}

func main() {
    eat(returnPair()) // this works
    eatWithSpice("pepper", returnPair()) // this does not
}

As a special case, if the return values of a function or method g are equal in number and individually assignable to the parameters of another function or method f, then the call f(g(parameters_of_g)) will invoke f after binding the return values of g to the parameters of f in order. The call of f must contain no parameters other than the call of g, and g must have at least one return value. If f has a final ... parameter, it is assigned the return values of g that remain after assignment of regular parameters. (http://golang.org/ref/spec#Calls)

Answer 1

You can assign those returning values first:

a, b := returnPair()
log.Printf("Returned %d %d", a, b

You can see an example in "Multiple return values from Go functions".

Using a multiple returning value directly in Println works though (since it accepts variadic parameters):

In your case: <kbd>play.golang.org</kbd>

package main

import "log"

func returnPair() (a int, b int) {
    return 42, 24
}
func main() {
    log.Println(returnPair())
}

Output:

2009/11/10 23:00:00 42 24