On Wed, 23 May 2018 03:03:18 -0700 (PDT)
lafolle <fghj...@gmail.com> wrote:
> Thanks Mathias for clearing this out.
>
> I reasoned this out by looking at the address to which `i` was
> allocated to, though I wanted to _peek_ inside the slice's header to
> be affirmative. But I can't clearly understand how to use unsafe
> pointer. Thanks for showing how to use it.
>
> One thing I don't understand is that why `i` is always allocated to
> same address? Is it to reduce allocations? Do other languages also
> do this?
Most languages do not have arrays as values and therefore this special
case does not apply to them. With respect to ordinary loops, yes,
that's the normal way to do it. In fact for typical loops that use
integer loop variables that live only for the duration of the loop,
there is no allocation. The variable is simply kept in a processor
register. Even the Go compiler does that when possible. It's easier to
understand when you look at a loop like this
for i := 0; i < 10; i++ {
...
}
The "i:=0" is only executed ONCE, at the very start of the loop. So
it's obvious that if an allocation is necessary, it occurs only once,
as neither "i<10" nor "i++" can cause an allocation.
Your loop is really just a fancy version of this same pattern.
MSB
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