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][1] **示例的结果与spec中描述不符** [**Order of evaluation**][2] 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. [1]: http://play.golang.org/p/kfzVt0YoSl [2]: http://golang.org/ref/spec#Order_of_evaluation