Ok, I am new to perl,  But do make a good effort I think.

Anyways, here is my problem:

$price = "2,450";

if ($price <= "99")
  {
  ....
  ....
  }

what happend is it thinks 2,450 is smaller than 99, i know this is
becouse of the comma.

My question is how do i remove the comma from a string?

please, any help would help.

Mike

  $price =~ tr/,//d;

Or, if you want to keep groups of three digits separated, Perl ignores _
inside numbers.  So you can do

  $price =~ tr/,/_/;

to turn $price into '2_450', then work with that.  That makes doing a
reverse tr back to commas trivial, should you need to redisplay $price
later with commas again.

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        ...The underscore only works within literal numbers                              
          specified in your program, not for strings functioning          
          as numbers or data read from somewhere else...

$_ = 2_345;   # A number, not a string
print $_+1;   # Prints 2346

$_ = '2_345'; # A string, not a number
print $_+1;   # Prints 3

It's my understanding that the _ is removed at assignment (or
compile time?)...

Hope this helps!

--Matthew

Oops, right you are.  Seems a silly way to have implemented things, but
that's the way it is.  Ignore my tr/,/_/ recommendation, please.

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        while (<DATA>) {
          print $_+1, "\n";
        }

        __DATA__
        077

... which prints `78', and not `0100'.

Code and data aren't the same thing.

Anyway, the underscores weren't allowed in literal constants until
recently, but changing the way string-to-number conversions are
performed in data would have broken many programs.

Problem 1 is: you don't use the -w option.
   -w would tell you: Argument "2,450" isn't numeric in le at ...

So you can rewrite the code to
$price = 2,450;
if ($price <= 99)
  {
  ....
  ....
  }

This will cause then error: Useless use of a constant in void context
at ...

So you can rewrite the code to
$price = 2450;    # or $price = 2.450; ?
if ($price <= 99)
  {
  ....
  ....
  }

Ronald

I guess my time in the Lisp world made me question that assumption. :)
Seriously, I think it's a reasonable goal that, where possible, code and
data *should* use the same formats and conventions.  And, indeed, I've
often wished that 077 and 0xCA in input data would parse as octal and hex
respectively.

: Anyway, the underscores weren't allowed in literal constants until
: recently, but changing the way string-to-number conversions are
: performed in data would have broken many programs.

That's the stronger argument, of course, though it's sad how every
language and OS become gradually encumbered by the weight of past
practice.  Then again, I suppose that's (one reason) why new languages and
OSs appear from time to time.

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and you'd discover that the zip code had been interpreted as `1089'.

It's much better to call an explicit conversion function if you want
the 1089.  In this case, the function is called `oct'.

And of course, it's not hard to build such a conversion function:

        if (numval("2,342") < 7) {
          ...
        }

As you pointed out, Lisp does have such features---all invoked through
explicit conversion functions of one kind or another.  The most
powerful and well-known of these conversion functions is `eval'.

Perl has `eval' too.  If you want underscores in your numbers, then

        if (eval "2_342" < 7) {
          ...
        }

will work just fine.

Well, one could argue that the zip code should be treated as a string
value, not a numeric value.  If treated as a string, the original
representation would be retained.  Only if the zip code were treated as an
operand in a numeric operation would the conversion occur.

But I agree in the general case that this could cause some very serious
problems.

: As you pointed out, Lisp does have such features---all invoked through
: explicit conversion functions of one kind or another.  The most
: powerful and well-known of these conversion functions is `eval'.

I was referring (a bit elliptically, true) more to Lisps use of list
representation for both data and code, and the resulting easy blurring of
the two.  The formats for external scalar representation are indeed
subject to similar explicit manipulation in Perl and Lisp.

: >it's sad how every language and OS become gradually encumbered by the
: >weight of past practice.
:
: While I would agree with you in general, I think that this is not a
: sad example.  I think this is an example of how a good designer can
: get things right the first time and not have to change them later.

Quite probably so wrt octal and hex interpretations, possibly not so wrt _
as a thousands separator, and certainly a minor enough nit (with easy
enough workarounds) that it does not noticeably dim Perl's brilliant glow.

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Removing the , from the string works fine (in this example).  

Consider:

#!/usr/bin/perl -w

$_ = '2,450';

if ( $_ < 99 ) {print "(1) Less than 99!\n";}
else           {print "(1) Greater than 99!\n";}

tr/,//d;

if ( $_ < 99 ) {print "(2) Less than 99!\n";}
else           {print "(2) Greater than 99!\n";}

__END__

Gives me:

Argument "2,450" isn't numeric in lt at temp line 5.
(1) Less than 99!
(2) Greater than 99!

Hope this helps!

--Matthew

  ;; Make a counter object that supports `increment' and `get' methods
  ;; Please pardon my syntax errors if there are any
  (defun make-counter ()
    ( let ((x 0))
      (lambda (operation)
       (cond ((eq operation 'increment)
              (setq x (+ x 1)))
             ((eq operation 'get)
              x)
             (t
              (error "Unknown operation: " (make-string operation)))
        )
    )))

   ;; Convenience methods for counters
   ;; Is x data?  Or is it code?  Who knows?  Who cares?
   (defun increment (x) (x 'increment))
   (defun get (x) (x 'get))

   ;; Try them out
   (setq c1 (make-counter))
   (setq c2 (make-counter))
   (increment c1)
   (increment c1)       ; Is c1 a data object?  Or a function?  Whatever!
   (increment c1)
   (get c2)             ; yields 0
   (get c1)             ; yields 3

But it seemed to me that your complaint didn't have anything to do
with this; instead it was about treatment of input data and of literal
constants in the source, and had a lot more to do with eval and
backquote and string->symbol and the like.  These are important
features of Lisp, but not nearly as central or as important to the
`data as code' notion as the use of closures is.

I sent followups to comp.programming since this no longer appears to
have anything to do with Perl.