Re: [DUG]: VB Like Case statement

[Matt Powell]

> In theory OO programming never needs a switch statement.

No, but it can be written and compiled a lot more efficiently using a
switch statement. It need not take O(n/2) comparisons to switch, either.
It is possible to take O(log n) comparisons:

case foo of
  0..3: blarg(1);
  4, 11: blarg(2);
  5: blarg(3);
  6-8: blarg(4);
  9: blarg(5);
  10: blarg(6);
end;

...can be compiled as:

   if foo >= 6 then goto 9;
0:
   if foo > 3 then goto 4;
   blarg(1);
4:
   if foo = 5 then goto 5;
   blarg(2);
   goto end;
5:
   blarg(3);
   goto end;
6:
   blarg(4);
   goto end;
9:
   if foo < 9 then goto 6;
   if foo >= 10 then goto 10;
   blarg(5);
   goto end;
10:
   if blarg = 11 then goto 4;
   blarg(6);
end:

...effectively performing a binary search for the number you want.

This sort of binary-select is not difficult to do automatically - you
just have to look out for multiple disjoint ranges (like 4,11) that
share blocks of code. Does anyone know if any compilers actually
implement this method?

- Matt
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