求值顺序

package main

import "fmt"

var a = 4

func main() {
    fmt.Println(a, add(), a) //Output:8 8 8
}

func add() int {
    a += 4
    return a
}    

goplay

示例的结果与spec中描述不符

Order of evaluation

When evaluating the operands of an expression, assignment, or return statement, all function calls, method calls, and communication operations are evaluated in lexical left-to-right order.

For example, in the assignment y[f()], ok = g(h(), i()+x[j()], <-c), k() the function calls and communication happen in the order f(), h(), i(), j(), <-c, g(), and k(). However, the order of those events compared to the evaluation and indexing of x and the evaluation of y is not specified.

Floating-point operations within a single expression are evaluated according to the associativity of the operators. Explicit parentheses affect the evaluation by overriding the default associativity. In the expression x + (y + z) the addition y + z is performed before adding x.