Update the Mac OS X situation.

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

diff --git a/pod/perlfaq4.pod b/pod/perlfaq4.pod
index 3b9cac6..27908d5 100644 (file)
--- a/pod/perlfaq4.pod
+++ b/pod/perlfaq4.pod
@@ -1,6 +1,6 @@
 =head1 NAME
 
-perlfaq4 - Data Manipulation ($Revision: 1.14 $, $Date: 2002/02/08 22:30:23 $)
+perlfaq4 - Data Manipulation ($Revision: 1.21 $, $Date: 2002/05/06 13:08:46 $)
 
 =head1 DESCRIPTION
 
@@ -135,7 +135,7 @@ functions is that it works with numbers of ANY size, that it is
 optimized for speed on some operations, and for at least some
 programmers the notation might be familiar.
 
-=item B<How do I convert Hexadecimal into decimal:>
+=item B<How do I convert hexadecimal into decimal:>
 
 Using perl's built in conversion of 0x notation:
 
@@ -214,6 +214,11 @@ Using Bit::Vector
 
 =item B<How do I convert from binary to decimal:>
 
+Perl 5.6 lets you write binary numbers directly with
+the 0b notation:
+
+       $number = 0b10110110;
+
 Using pack and ord
 
     $decimal = ord(pack('B8', '10110110'));
@@ -346,6 +351,20 @@ 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?
@@ -581,7 +600,7 @@ 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?
@@ -690,6 +709,11 @@ 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:
@@ -1125,11 +1149,11 @@ 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
@@ -1139,7 +1163,7 @@ 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;
 
@@ -1316,28 +1340,21 @@ lists, or you could just do something like this with an array:
 If you either have Perl 5.8.0 or later installed, or if you have
 Scalar-List-Utils 1.03 or later installed, you can say:
 
-        use List::Util 'shuffle';
+    use List::Util 'shuffle';
 
        @shuffled = shuffle(@list);
 
-If not, you can use this:
+If not, you can use a Fisher-Yates shuffle.
 
-    # fisher_yates_shuffle
-    # generate a random permutation of an array in place
-    # As in shuffling a deck of cards
-    #
     sub fisher_yates_shuffle {
         my $deck = shift;  # $deck is a reference to an array
         my $i = @$deck;
-        while (--$i) {
+        while ($i--) {
             my $j = int rand ($i+1);
             @$deck[$i,$j] = @$deck[$j,$i];
         }
     }
 
-And here is an example of using it:
-
-    #
     # shuffle my mpeg collection
     #
     my @mpeg = <audio/*/*.mp3>;
@@ -1885,9 +1902,9 @@ 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>