Do/while correct answer loop

I don't often use a do-while loop, but when I was writing my Animals program, I found this to be a useful little trick for interactive input that needs a certain letter.

do {
  print "\nDid I guess your animal?\n\n";
} while ($answer=<STDIN>) !~ /^[YN]/i;

## OR

do {
  print "\nDo you want to <P>lay again or <Q>uit?\n\n";
} while ($answer=<STDIN>) !~ /^[PQ]/i;
[download]

The three newlines help to clear out the users input and make a nicer looking response if they fail to answer with a correct letter. Since $answer has already been set, after the loop you can say:

if ($answer =~ /^P/i) {
  ## Code for P here
}
## Add some elsifs if > 2 choices
else { 
  ## No need to check the final letter
  ## Code for Q here
}
[download]

Comment on Do/while correct answer loop Select or Download Code

Replies are listed 'Best First'.
RE: Do/while correct answer loop by merlyn (Sage) on May 12, 2000 at 19:49 UTC
I tend to avoid the `do {...} while $cond` loop because it's not a real loop. You can't use next/last/redo with it. As I said in this week's poll, I use a naked block with `last` and `redo`: `{ stuff more stuff last if $cond; # middle exit still more stuff again more stuff redo if $cond; # repeat as long as $cond is true }` [download] This way you can name the loop (for multiple break-outs). If you want `next OUTERLOOP` to work, you merely next to add additional `continue` block: `OUTERLOOP: { blah while ($foo) { blah next OUTERLOOP if $cond; blah } blah } continue { redo if $cond; }` [download] Naked blocks are fun! -- Randal L. Schwartz, Perl hacker	[reply] [d/l] [select]
RE: RE: Do/while correct answer loop by turnstep (Parson) on May 12, 2000 at 19:54 UTC
Yes, but when else am I going to use poor old "do/while?" :) I admit, the bare block does look better: `{ print "\nDo you want to <P>lay again or <Q>uit?\n\n"; ($answer=<STDIN>) =~ /^[PQ]/i or redo; }` [download]	[reply] [d/l]