foreach

[Manu via Digitalmars-d]

On 13 June 2014 13:42, Steven Schveighoffer via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On Thu, 12 Jun 2014 23:34:27 -0400, Manu via Digitalmars-d
> <digitalmars-d at puremagic.com> wrote:
>
>> On 13 June 2014 13:04, Daniel Murphy via Digitalmars-d
>> <digitalmars-d at puremagic.com> wrote:
>>>
>>>
>>> i,j,k,etc work just fine.  Are you really nesting your loops that deeply?
>>
>>
>> Giving explicit names pollutes the local namespace, and the point
>> below about unreferenced variable warnings if you give explicit names.
>
>
> i, j, k are traditionally loop variables. People have been using them for
> decades without conflicting their other variables.
>
>>>
>>> The compiler's optimizer will do that just fine.
>>
>>
>> Not necessarily. The range might be a lib, and non-pure. The compiler
>> can't optimise/inline/eliminate the call if it doesn't have code.
>> In my experience this is common, I frequently wrap C api's in D-style
>> ranges. Potentially a lot of unnecessary calls to
>> C_API_GetItem(itemIndex).
>
>
> 2 options:
>
> foreach(i; 0..r.walkLength)
> {
> }

walkLength might not be known ahead of time. Lists?


> or
>
> while(!r.empty)
> {
>    r.popFront();
> }

This modifies 'r', which foreach doesn't do. I'm forced to capture a
copy for the sake of the loop? Sounds like a likely place for bugs to
emerge... convert foreach code to this code as an optimisation, and a
consecutive loop now terminates immediately changing program
behaviour...