Not just your C; C sucks in general. As a case in point, the C case statement is next-to-worthless, because fallthrough is not usually what you want. There are cases for it, but they're the exception rather than the rule. As a result, you end up needing to insert break statements at nearly every case, at which point you have barely less typing to do than with a nested if structure. Perl's elsif is actually an improvement on this.

The case statement in Inform (and even SELECT CASE in BASIC) is much more useful. If Perl ever gets a case, I hope the breaks are implied; otherwise I'll end up never using it.

Most of the cases where you want the fallthrough, it's because what you want is actually not a case statement, but some other structure. This is a perfect example. What it's doing is not really unique to each case; there are some minor variations, but what you really want is a loop.

Others have done efficient things (and I particularly like the pack solution), but I'll add my own translation, on the grounds that it is straightforward and legible... 

{ my @shiftby = (0, 8, 16, 24, 0, 8, 16, 24, 8, 16, 24); 
  my $l;
  foreach $l (reverse 1 .. $len) {
     if    ($l>8) {   $c += $k[$l-1]<<$shiftby[$l]; }
     elsif ($l>4) {   $b += $k[$l-1]<<$shiftby[$l]; }
     else         {   $a += $k[$l-1]<<$shiftby[$l]; }
  }
}

[download]

I've reduced the number of += operations to three, and it is easy to see where the similarities and the differences are. The if/elsif/else makes it stand out when you are incrementing a different variable. (When I first looked at the thing, I thought the same variable was being incremented ten times.) Even better, it is clear how @k is being used; before, you had to look at each line and compare the index to @k with the case number, if you wanted to know if there were any deviations from the pattern; here it's clear there are none; $l-1 is always $l-1.

@shiftby could probably also be replaced with an arithmetic expression, but I'm not sure that would improve clarity.

 --jonadab

In reply to Re: Eek! goto? by jonadab
in thread Eek! goto? by BrowserUk

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