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(dragonchild) 8: Fear of Large Languages (was: "Would you use goto")

by dragonchild (Archbishop)
on Dec 07, 2001 at 18:46 UTC ( #130196=note: print w/replies, xml ) Need Help??


in reply to Re (tilly) 6: Fear of Large Languages (was: "Would you use goto")
in thread Would you use 'goto' here?

As I said earlier in the thread, continue block or function call should have been what I did. But, I felt that I didn't want to hide the meat of the script in a function call and continue blocks are "a lesser-known" feature of Perl, similar to "goto &SUB".

I guess my point is that I have a reason for not wanting to do either of the "correct" ways, and one of those reasons is the very reason most people gave Ovid to not use "goto &SUB", even though it was the absolute correct syntax to use in his specific case.

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  • Comment on (dragonchild) 8: Fear of Large Languages (was: "Would you use goto")

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Re: (danger) 9: Fear of Large Languages (was: "Would you use goto")
by danger (Priest) on Dec 08, 2001 at 05:27 UTC
    I guess my point is that I have a reason for not wanting to do either of the "correct" ways

    The general 'better known' vs 'lesser known' argument can be summarized as: if X is a problem can be solved with either construct A or B, and if A is assumed to be more widely known, then we should choose to implement using A. A reasonably fair argument. Counter examples obviously would occur when say memory or speed is crucial and B is clearly optimal with regard to these additional constraints. But we are talking about readability optimization here right?

    However, I argue that this does not apply to using goto rather than continue (even if goto is indeed more known than continue). Why? Because familiarity with goto LABEL doesn't really help the reader understand the logical structure of the code.

    The logical elements of the code should be mirrored in the structural elements of the code as much as possible. This means jump destinations should mesh with the boundaries of the structural elements (block boundaries), and things like next, last, and redo do so. Using goto DONE introduces a synthetic, non-structural element to delimit a logical element of the code. This places an additional mental burden on the reader who now must maintain a dangling mental reference to a goto-label because the code structure itself provides no cue about the limits of the current logical element.

    Thus while using goto may relieve your readers of having to look up continue or to learn about bare-blocks and loop control statements (as per one of tilly's suggestions), it doesn't relieve them of the mental burden of understanding the logical usage of the goto in the current code.

    As an aside, another alternative for the particular code example you gave would be to use the ?: operator and avoid having both an 'if' and an 'else' block:

    for my $foo (@bars) { # ... do preliminary stuff # ... if ($foo =~ /baz/i ? $foo eq uc $foo: $foo ne uc $foo) { # ... do conditional stuff # ... } # ... do remaining stuff # ... }

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