First many thanks for giving the internal perspective (I was hoping you would take the time to do this!). I am not terribly familiar with the Perl source code, but it seems that the op code names in opcode.h are consistent with your point about map being a shorthand for a looping op-tree. In EXTCONST char* const PL_op_name[], not only does "map" have an op code name, but I also see two others: "mapstart" and "mapwhile". Are these the opcodes for the loop you are talking about? (sometimes header files can be deceiving if you don't know the code base well)

grep acts like map with regard to returns. It also seems to treat its block like a loop and, not surprisingly, it too has three op code names: "grep", "grepstart", and "grepwhile".

On the other hand, I'm thinking that sort may be implemented like something closer to function. Unlike "map" or "grep" it has only the one op-code "sort". Also, as mentioned earlier on this thread, it treats returns as if the block was an eval {} or anonymous subroutine. What is your take given your greater experience with internals?

Also, is there any guideline or rule of thumb that can be used to determine how routines listed in index-functions are going to treat a block? It seems like there ought to be something other than testing code samples, knowing internals, or word-of-mouth from other Perl programmers.

Best, beth

In reply to Re^2: map and return by ELISHEVA
in thread map and return by ELISHEVA

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