[m-rev.] for review: mercury implementation of string.m
Fergus Henderson
fjh at cs.mu.OZ.AU
Thu Jun 20 07:36:48 AEST 2002
On 13-Jun-2002, Peter Ross <pro at missioncriticalit.com> wrote:
> +:- pragma foreign_proc("MC++", string__to_char_list(Str::in, CharList::uo),
> + [will_not_call_mercury, promise_pure, thread_safe], "{
> + MR_Integer length, i;
> + MR_Word tmp;
> + MR_Word prev;
> +
> + length = Str->get_Length();
> +
> + MR_list_nil(prev);
> +
> + for (i = length - 1; i >= 0; i--) {
> + MR_list_cons(tmp, __box(Str->get_Chars(i)), prev);
> + prev = tmp;
> + }
> + CharList = tmp;
> +}").
This code is broken. It will return an uninitialized variable
when length == 0.
> +:- pragma foreign_proc("MC++", string__to_char_list(Str::uo, CharList::in),
> + [will_not_call_mercury, promise_pure, thread_safe], "{
> + System::Text::StringBuilder *tmp;
> + MR_Char c;
> +
> + tmp = new System::Text::StringBuilder();
> + while (1) {
> + if (MR_list_is_cons(CharList)) {
> + c = System::Convert::ToChar(MR_list_head(CharList));
> + tmp->Append(c);
> + CharList = MR_list_tail(CharList);
> + } else {
> + break;
> + }
> + }
That loop should be written as
while (MR_list_is_cons(CharList)) {
c = System::Convert::ToChar(MR_list_head(CharList));
tmp->Append(c);
CharList = MR_list_tail(CharList);
}
--
Fergus Henderson <fjh at cs.mu.oz.au> | "I have always known that the pursuit
The University of Melbourne | of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh> | -- the last words of T. S. Garp.
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