Perl Variables: Hash

1. Perl Variables:Hash Web Programming

2. Hash (Associative Array) • Syntax • key and value pair • %hash = (key1, value1, key2, value2, ….); • Hash Elements • $hash{keyN} = valueN; • Assigning values • intialization • %hash = (element list); • %hash = @array; • %hash = (key1=>value1, key2=>value2, …); • assigning values to individual hash element • $hash{“key1”} = “value1”; • Hash elements are stored in a random order  Example script Web Programming

3. Hash Functions • @keys = keys (%hash); • return an array of hash keys • @values = values (%hash); • return an array of hash values • (key,value) = each (%hash); • return a key-value pair sequentially • delete ($hash{key}); • deletes a hash element • exists ($hash{key}) • returns true if key exists in %hash  Example script Web Programming

4. Printing Hash • print %hash; • hash is collapsed into an array and then printed • i.e. print @hash • print join (“:”,%hash); • hash collapsed into array is joined and printed • i.e. print join (“:”,@hash) • while (($key, $value) = each %hash) { print “$key=$value\n”;} • foreach $key (sort keys %hash) { print “$key=$hash{$key}\n”; }  Example script Web Programming

5. Hash Examples • Word Countopen(IN,$file) || die “can’t open $file”;@lines=<IN>;close IN;foreach $line(@lines) { @words= split(/ +/,$line); foreach $wd(@words) { $wdcnt{$wd}++; }} Example script Web Programming