来自go来源的代码是什么意思？ 像（*（* float32）（v.ptr））

Question

In reflection package I see the code like

    return float64(*(*float32)(v.ptr))

What is *(*float32)(v.ptr)? I don't have any ideas

Answer 1

Let's unwrap the expression. We'll take it from innermost to outermost, since that's the order it's evaluated:

(*float32)(v.ptr)

Convert v.ptr to *float32, a pointer to a float32.

*(*float32)(v.ptr)

Dereference that pointer, giving us a float32 value.

float64(*(*float32)(v.ptr))

Convert the float32 value to a float64 value.

So, whatever v.ptr is, it's converted to a float32 pointer, dereferenced, and then converted to float64, and returned.