Re: cl-dolist, dolist, cl-return,

[Emanuel Berg]

Barry Margolin <barmar@alum.mit.edu> writes:

>> The reason I asked is the C for loop, which looks
>> like this in C99 style:
>> 
>>     for (int i = 0; i < a_size; i++) { a[i] = ... ; }
>> 
>> But sometimes, people are tempted to do like this:
>> 
>>     for (int i = 0; i < sizeof(a)/sizeof(a[0]); i++) { a[i] = ... ; }
>
> You're making the wrong analogy. The list parameter of
> dolist is equivalent to the initialization part of
> the "for", not the repetition or update parts. So if
> you did:
>
> for (int i = func(x); ...)
>
> you wouldn't expect func(x) to be called every time
> through the loop, would you?
>
> The C equivalent of dolist is:
>
> for (list_ptr* p = <list expr>; p; p = p->next) { ...
> }
>
> As above, you wouldn't expect <list expr> to be
> evaluated each time.

That's exactly right!

Very nice - you even put the asterisk with the
variable type and not its name.

I was about to say this discussion is meaningless as
several posts ago it was clear the list isn't
re-evaluated, which was the intuition as well, but now
I've changed my mind, when you put things this way,
please go on.

-- 
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http://user.it.uu.se/~embe8573