I think it's avoiding those "off by one" corrections that helps. Because of the interpretive nature, ($x+1) has a certain amount of overhead, compared to the machine INCrement instruction of a register. But "big" instructions like map and foreach have spread the overhead over a lot of work, so it is not noticable.

I conjecture that map is good because it knows that the output list will be the same size as the input list, and can set things up properly ahead of time, as opposed to push'ing each element as a separate instruction

Very clever how you initialize $delta to avoid the shift and "+1" corrections. Many thanks for illustrating your techniques.

—John

In reply to Re^4: Perl Drag Racing - sum/delta list by John M. Dlugosz
in thread Perl Drag Racing - sum/delta list by John M. Dlugosz

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