Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I am having a problem with passing a hex number argument to a function that takes string argument. I do not want to change those function to expect hex number because then I'll have to make tons of changes. To be more specific: 
# 
my $num = 0x100;
my $chr = string of $num;      # not sure what this should be
call_f2($chr);
sub call_f2{
  my $str = shift;
  &f2($str);
}
sub f2 {
  my $str = shift;
  print ($str);
}
# I want to print 100, is it possible?

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Replies are listed 'Best First'.
Re: passing hex argument as string
by pg (Canon) on Nov 04, 2003 at 02:43 UTC

    One way is to use sprintf:

    use strict;
use warnings;

my $bar = 0x100;
print foo(sprintf("%x",$bar));

sub foo {
    return shift() . "abc";
}

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    You can check out perlfunc for details of this function.

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Re: passing hex argument as string
by batkins (Chaplain) on Nov 04, 2003 at 02:44 UTC
    Well, I'm not sure I'm getting what you're getting at. First of all, the call_f2 sub is entirely superfluous. Now you're comment says that you're trying to print 100. I'm not sure what that means. If you want to print $num in base-10, you should be able to just print it out. If you want to print it in hex (base-16), try: 
    printf "%x", $chr;

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    Are you sure it was a book? Are you sure it wasn't.....nothing?
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      yes I am familiar with printf function. But I can not do that. Beccause the function that takes $chr is *FIXED*, and I can not change it. So what I want is a function that: # takes a hex number 0xff # returns string "ff" and NOT 255
[reply]
        That's what 
        sprintf("%x", $hexnum)

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        does. If $hexnum is 0xdeadbeef, the sprintf will return "deadbeef". (Use %X instead of %x if you want "DEADBEEF".)

        (updated to correctly say sprintf instead of printf)

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Re: passing hex argument as string
by TomDLux (Vicar) on Nov 04, 2003 at 03:25 UTC

    The hex number exists only on the right hand side of line 1; the value stored in $num is 0...0100000000, popularly known as 256.

    If f2 doesn't do any calculations with the argument, only print it out, you might be able to pass in the number as a hex string:

    f2( sprintf "0x%0x", $num );

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    --
    TTTATCGGTCGTTATATAGATGTTTGCA

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Re: passing hex argument as string
by ysth (Canon) on Nov 04, 2003 at 11:44 UTC
    The simple answer is to create the string with sprintf "%x". There's more information about controlling the hexadecimal formating in the Categorized Q&A How do I convert from decimal to hexidecimal?.

    (updated to correct my hexi->hexa but leave the Q link wrong)

    That's the end of the practical answer. Flight of fancy follows...

    Read more... (2 kB)
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