Re: [MacPerl] Commify and "1 while" syntax

[Kevin van Haaren <kevinv@hockey.net>]

At 7:43 AM -0700 1999/5/31, Darryl Tang wrote:
>Hi everyone,
>
>I was racking my brain last night over this one:
>
>	1 while ($number =~ s/^(-?\d+)(\d{3})/$1,$2/);
>
>This will add commas into a number string and is similar to the example in
>the Programming Perl book (2d Edition) on page 74.  I understand that the
>"1 while" will make Perl repeatedly match the regular expression and apply
>it to $number, resulting in commas in the appropriate spots.
>
>My question is what is the "1" preceding "while" for?  You can change the
>"1" to something else (e.g. "2", or "FOO" or "x") and it still works
>properly, but you can't eliminate it entirely.  I can't find any
>explanation as to what this string preceding the while is supposed to do.
>I can take it on faith that this is appropriate syntax, but I like to
>understand what is going on!
>
>Thanks for any help.
>
>Darryl Tang
>

Basically it's the argument for the while statement.

It's the same as:

while (1) {
	do stuff;
}


The construct is similar to:

do this if (this is true);

As long as whatever you put there is true, the while statement will work.
Eliminating it makes it undef, therefore the while is false and skips the
statement (or it's evaluating the $number =~ construct for true/falseness,
I'm not sure).

I believe the ability to put the operation before the if/while statement
was put there so "the important stuff" is first on the line and seen first.
I use it a lot with the if statements, but I'm not sure it increases
readability in a while statement (but then I'm used to the "old" style
programming languages).

Kevin

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