in reply to Speeding up unshift

I am very frustrated in that your patch looks simpler than my attempt, and yet I'm not sure I understand, probably because the AvMAX() and AvFILLp() don't seem to be documented well enough for me to figure out what they're doing.
if (num) { i = AvFILLp(av); /* Create extra elements */ /**/ slide = i > 0 ? i : 0; /**/ num += slide; av_extend(av, i + num); AvFILLp(av) += num; ary = AvARRAY(av); Move(ary, ary + num, i + 1, SV*); do { ary[--num] = &PL_sv_undef; } while (num); /* Make extra elements into a buffer */ /**/ AvMAX(av) -= slide; /**/ AvFILLp(av) -= slide; SvPVX(av) = (char*)(AvARRAY(av) + slide); } }
Why do you add num to AvFILLp() (which is the original num with slide added to it) only to then SUBTRACT slide? And what is AvMAX()?!

And I would personally suggest using the heuristic for slide that I had in my code -- namely:
slide = (i < num && i > 0) ? i : num;
Anyway. Sigh. I'm not annoyed at you, but at my inability to patch something that shouldn't have been such a well of annoyance.

japhy -- Perl and Regex Hacker