in reply to Using Regular Expressions to Simulate sprintf() function - One Liner Challenge

First a couple of points that may or may not be obvious:

I quickly threw together a regex (included below) just for my amusement, but then got somewhat confused by the specification and the various interpretations so far. If nothing else this is an interesting exercise in both how different people will interpret the same request, and how many different tests are needed to check the behaviour of even this simple concept. I've added the samples suggested by Incognito and jeffa, as well as one of my own. I haven't bothered to fix my solution, but as you can see, none duplicated sprintf. 

value|precision     sprintf   Incognito   Albannach       jeffa
 '123.45678'|3:     123.457     123.456     123.456         123
      '12.4'|1:        12.4        12.4        12.4          12
          ''|0:           0
      '3.14'|5:     3.14000     3.14000     3.14000    00003.14
         '1'|5:     1.00000     1.00000     1.00000       00001
        '.5'|0:           1
        '10'|5:    10.00000    10.00000    10.00000       00010
  '12.45435'|0:          12          12          12          12
       '100'|5:   100.00000   100.00000   100.00000       00100
        '3.'|0:           3           3           3           3
      '1000'|5:  1000.00000  1000.00000  1000.00000       01000
     '12.56'|0:          13          12          12          12

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was produced by 
use strict;
#use warnings; # sprintf doesn't like nulls as values

my %test = ( ''        => 0,
             '.5'      => 0,
             1         => 0,
             '3.'      => 0,
             100       => 4,
             12.4      => 1,
             12.56     => 0,
             12.45435  => 0,
             123.45678 => 3,
             3.14      => 5,
             1         => 5,
             10        => 5,
             100       => 5,
             1000      => 5,
           );

printf('value|precision'."%12s"x4 ."\n", qw(sprintf Incognito Albannac
+h jeffa));
while (my ($v,$p)= each %test) {
  printf("%14s:","'$v'|$p");
  printf("%12s"x4 ."\n", 
    sprintf("%.${p}f", $v), Incognito($v,$p), Albannach($v,$p), jeffa(
+$v,$p) );
}

sub Albannach {
  my($val, $pre) = @_;
  $val =~ s/(\d*)(\.?)(\d*)/"$1".($pre?'.':'').substr($3.'0'x$pre, 0, 
+$pre)/e;
  $val;
}

sub Incognito {
  my ($strValue,$strPrecision) = @_;

  # Pad the number with a bunch of zeros
  $strValue =~ s/^(\d*)\.?(\d*)$/${1}.${2}000000000/;

  # Remove all but the first '$strPrecision' digits that immediately
  # trail the decimal point.
  my $strDefaultPrecision = 2;
  $strPrecision = ($strPrecision >= 0) ? $strPrecision : $strDefaultPr
+ecision;
  if ($strPrecision == 0) {
    $strValue =~ s/^(\d*)\.?\d*$/$1/;
  } else {
    $strValue =~ s/^(\d*\.\d{$strPrecision})\d*$/$1/;
  }
  $strValue;
}

sub jeffa {
  my ($str,$pad) = @_;
  my ($add,$right);

  ($str,$right) = split('\.',$str,2);
  $right = ($right) ? ".$right" : '';
  $add   = $pad - length($str);

  return $str if $add < 1;
  return ('0' x $add) . $str . $right;
}

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--
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Re: Re: Using Regular Expressions to Simulate sprintf() function - One Liner Challenge
by Incognito (Pilgrim) on Nov 07, 2001 at 00:05 UTC

    Yes, good point... We're not really simulating sprintf(), but just the part where we take a number and add a decimal place at one part of a number and format it to our liking...

    I think a lot of people didn't notice that the Perl code was just a snippet of what was in the actual function, and that I didn't provide the entire thing... if we examine the JavaScript version, we will notice that it handles the special cases: 

      strValue += "";      // Convert any digits to string
  if (! strValue) { strValue = "0"; }  // Convert empty string to 0

  // Set any non-numeric values to 0
  if (! strValue.match (/^\d+\.?$|\d+\.?\d*$|\d*\.?\d+$/)) { strValue 
+= "0"; }

  // Add a leading 0 to any numbers starting with a decimal point
  if (strValue.match (/^\./)) { strValue = "0" + strValue; }

    [download]

    So what we really have (without actually provided the entire function :) is: 

    value|precision     sprintf   Incognito   Albannach       jeffa      r
+ob_au
 '123.45678'|3:     123.457     123.456     123.456         123     12
+3.457
      '12.4'|1:        12.4        12.4        12.4          12       
+ 12.4
          ''|0:           0           0                               
+    0
      '3.14'|5:     3.14000     3.14000     3.14000    00003.14     3.
+14000
         '1'|5:     1.00000     1.00000     1.00000       00001     1.
+00000
        '.5'|0:           0           0                               
+    1
        '10'|5:    10.00000    10.00000    10.00000       00010    10.
+00000
  '12.45435'|0:          12          12          12          12       
+   12
       '100'|5:   100.00000   100.00000   100.00000       00100   100.
+00000
        '3.'|0:           3           3           3           3       
+    3
      '1000'|5:  1000.00000  1000.00000  1000.00000       01000  1000.
+00000
     '12.56'|0:          13          12          12          12       
+   13

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