Differences

This shows you the differences between two versions of the page.

--- notes:perl_cheat_sheet [2026/11/02 09:10]
191.242.44.87 old revision restored (2026/08/06 06:49)
+++ notes:perl_cheat_sheet [2026/11/03 05:52] (current)
37.122.152.241 old revision restored (2026/08/06 11:23)
@@ Line 62: / Line 62: @@
   * List functions may return different scalars - array variables return number of elements. The ''scalar'' function forces a scalar context e.g. for print function.
+===== Hashes =====
+  * A hash is a list indexed by a string (key) - a collection of key-value pairs. ''%hash'' has its own namespace.
+  * Uses scalable, efficient algorithms. Used to be called associative arrays.
+  * ''$hash{$some_key}'' to access a value (curly-braces instead of square braces).
+  * Assigning a hash to an array unwinds (flattens) it.
+  * To initialize a hash :<code perl>%some_hash = ('a', 1, 'b', 2, 'c', 3);
+%some_hash = ( 'a' => 1, 'b'=>2, 'c'=>3,);</code>
+  * When using a big arrow (a fat-comma) or when accessing a value, simple keys don't have to be quoted (barewords) e.g. <code perl>%some_hash = ( a => 1}; $some_hash{a};</code>
+  * ''%revhash = reverse %hash'' to reverse a hash (for non-unique values, last one wins).
 ===== Control Structures =====
@@ Line 103: / Line 113: @@
 open BEDROCK, '>fred' || die "Cannot open fred: $!";
 open LOG, '>>:encoding(UTF-8)','logfile'; # for perl >= 5.6
-open BEDROCK, '>:crlf', $file_name; # DOS-formatted output
+open my $bedrock, '>:crlf', $file_name; # DOS-formatted output
 binmode STDOUT, ':encoding(UTF-8)';</code>
+  * ''select'' can be used to change default output filehandle. ''$| = 1;'' unbuffers currently selected output.
 ===== User Subroutines =====

DokuWiki

Site Tools

Differences

Page Tools