Whitespace tweaks.

[p5sagit/p5-mst-13.2.git] / pod / perlfaq4.pod

diff --git a/pod/perlfaq4.pod b/pod/perlfaq4.pod
index 9d19337..b530516 100644 (file)
--- a/pod/perlfaq4.pod
+++ b/pod/perlfaq4.pod
@@ -1,12 +1,11 @@
 =head1 NAME
 
-perlfaq4 - Data Manipulation ($Revision: 1.11 $, $Date: 2002/01/11 02:31:20 $)
+perlfaq4 - Data Manipulation ($Revision: 1.19 $, $Date: 2002/03/11 22:15:19 $)
 
 =head1 DESCRIPTION
 
-The section of the FAQ answers questions related to the manipulation
-of data as numbers, dates, strings, arrays, hashes, and miscellaneous
-data issues.
+This section of the FAQ answers questions related to manipulating
+numbers, dates, strings, arrays, hashes, and miscellaneous data issues.
 
 =head1 Data: Numbers
 
@@ -123,7 +122,7 @@ Perl numbers whose absolute values are integers under 2**31 (on 32 bit
 machines) will work pretty much like mathematical integers.  Other numbers
 are not guaranteed.
 
-=head2 How do I convert between numeric representations:
+=head2 How do I convert between numeric representations?
 
 As always with Perl there is more than one way to do it.  Below
 are a few examples of approaches to making common conversions
@@ -347,6 +346,20 @@ random numbers, but this takes quite a while.  If you want a better
 pseudorandom generator than comes with your operating system, look at
 ``Numerical Recipes in C'' at http://www.nr.com/ .
 
+=head2 How do I get a random number between X and Y?
+
+Use the following simple function.  It selects a random integer between
+(and possibly including!) the two given integers, e.g.,
+C<random_int_in(50,120)>
+
+   sub random_int_in ($$) {
+     my($min, $max) = @_;
+      # Assumes that the two arguments are integers themselves!
+     return $min if $min == $max;
+     ($min, $max) = ($max, $min)  if  $min > $max;
+     return $min + int rand(1 + $max - $min);
+   }
+
 =head1 Data: Dates
 
 =head2 How do I find the week-of-the-year/day-of-the-year?
@@ -582,7 +595,7 @@ really does work:
     @( = ('(','');
     @) = (')','');
     ($re=$_)=~s/((BEGIN)|(END)|.)/$)[!$3]\Q$1\E$([!$2]/gs;
-    @$ = (eval{/$re/},$@!~/unmatched/);
+    @$ = (eval{/$re/},$@!~/unmatched/i);
     print join("\n",@$[0..$#$]) if( $$[-1] );
 
 =head2 How do I reverse a string?
@@ -691,6 +704,11 @@ integers:
     while ($string =~ /-\d+/g) { $count++ }
     print "There are $count negative numbers in the string";
 
+Another version uses a global match in list context, then assigns the
+result to a scalar, producing a count of the number of matches.
+
+       $count = () = $string =~ /-\d+/g;
+
 =head2 How do I capitalize all the words on one line?
 
 To make the first letter of each word upper case:
@@ -976,7 +994,7 @@ in the indentation.
             would deliver us. You are a liar, Saruman, and a corrupter
             of men's hearts.  --Theoden in /usr/src/perl/taint.c
         FINIS
-    $quote =~ s/\s*--/\n--/;
+    $quote =~ s/\s+--/\n--/;
 
 A nice general-purpose fixer-upper function for indented here documents
 follows.  It expects to be called with a here document as its argument.
@@ -1126,11 +1144,11 @@ designed to answer this question quickly and efficiently.  Arrays aren't.
 
 That being said, there are several ways to approach this.  If you
 are going to make this query many times over arbitrary string values,
-the fastest way is probably to invert the original array and keep an
-associative array lying about whose keys are the first array's values.
+the fastest way is probably to invert the original array and maintain a
+hash whose keys are the first array's values.
 
     @blues = qw/azure cerulean teal turquoise lapis-lazuli/;
-    undef %is_blue;
+    %is_blue = ();
     for (@blues) { $is_blue{$_} = 1 }
 
 Now you can check whether $is_blue{$some_color}.  It might have been a
@@ -1140,7 +1158,7 @@ If the values are all small integers, you could use a simple indexed
 array.  This kind of an array will take up less space:
 
     @primes = (2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31);
-    undef @is_tiny_prime;
+    @is_tiny_prime = ();
     for (@primes) { $is_tiny_prime[$_] = 1 }
     # or simply  @istiny_prime[@primes] = (1) x @primes;
 
@@ -1886,9 +1904,9 @@ Assuming that you don't care about IEEE notations like "NaN" or
    if (/^-?\d+$/)       { print "is an integer\n" }
    if (/^[+-]?\d+$/)    { print "is a +/- integer\n" }
    if (/^-?\d+\.?\d*$/) { print "is a real number\n" }
-   if (/^-?(?:\d+(?:\.\d*)?|\.\d+)$/) { print "is a decimal number" }
+   if (/^-?(?:\d+(?:\.\d*)?|\.\d+)$/) { print "is a decimal number\n" }
    if (/^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/)
-                       { print "a C float" }
+                       { print "a C float\n" }
 
 If you're on a POSIX system, Perl's supports the C<POSIX::strtod>
 function.  Its semantics are somewhat cumbersome, so here's a C<getnum>
@@ -1965,7 +1983,7 @@ the PDL module from CPAN instead--it makes number-crunching easy.
 
 =head1 AUTHOR AND COPYRIGHT
 
-Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington.
+Copyright (c) 1997-2002 Tom Christiansen and Nathan Torkington.
 All rights reserved.
 
 This documentation is free; you can redistribute it and/or modify it