GO的fmt.Println((1+8)/2)为什么是4，不是4.5？

Question

fmt.Println("见证奇迹的时刻到了，(1 + 8) / 2 = ", (1+8)/2)

Answer 1

go：整数除以浮点数的问题

为什么你会有“两个 int 类型相除，结果会自动转换为 float ”的想法。

Answer 2

golang 里 untyped contants 的运算结果类型确定方式如下(https://golang.org/ref/spec#C...：

Any other operation on untyped constants results in an untyped constant of the same kind; that is, a boolean, integer, floating-point, complex, or string constant. If the untyped operands of a binary operation (other than a shift) are of different kinds, the result is of the operand's kind that appears later in this list: integer, rune, floating-point, complex. For example, an untyped integer constant divided by an untyped complex constant yields an untyped complex constant.

这里大家都是 integer ，所以结果也是 integer.

注意对于有类型的，规则还不太一样(https://golang.org/ref/spec#A...：

Arithmetic operators apply to numeric values and yield a result of the same type as the first operand.

Answer 3

PHP这种弱类型才会自动转换类型

Answer 4

强类型都是砍掉小数，不会变浮点数，除非你明确指明

float32(8+1)/2