[Openwebwork-cvs] webwork2: added fisher_yates_shuffle() inplace-randomization routine.

[Sam H. v. a. <act...@de...>]

Log Message:
-----------
added fisher_yates_shuffle() inplace-randomization routine.

Modified Files:
--------------
    webwork2/lib/WeBWorK:
        Utils.pm

Revision Data
-------------
Index: Utils.pm
===================================================================
RCS file: /webwork/cvs/system/webwork2/lib/WeBWorK/Utils.pm,v
retrieving revision 1.59
retrieving revision 1.60
diff -Llib/WeBWorK/Utils.pm -Llib/WeBWorK/Utils.pm -u -r1.59 -r1.60
--- lib/WeBWorK/Utils.pm
+++ lib/WeBWorK/Utils.pm
@@ -74,6 +74,7 @@
 	cryptPassword
 	dequote
 	undefstr
+	fisher_yates_shuffle
 	sortByName
 );
 
@@ -721,6 +722,18 @@
 
 sub undefstr($@) {
 	map { defined $_ ? $_ : $_[0] } @_[1..$#_];
+}
+
+# shuffle an array in place
+# Perl Cookbook, Recipe 4.17. Randomizing an Array
+sub fisher_yates_shuffle {
+	my $array = shift;
+	my $i;
+	for ($i = @$array; --$i; ) {
+		my $j = int rand ($i+1);
+		next if $i == $j;
+		@$array[$i,$j] = @$array[$j,$i];
+	}
 }
 
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