Recipes for PDSC #1:
Lists of Lists

by Tom Christiansen
< tchrist@perl.com >

release 0.1 (untested, may have typos)
Sunday, 1 October 1995

Note

Please see the expanded version of this document for a much more elaborate description of the recipes used herein.

Declaration of a LIST OF LISTS:

@LoL = ( 
       [ "fred", "barney" ],
       [ "george", "jane", "elroy" ],
       [ "homer", "marge", "bart" ],
     );

Generation of a LIST OF LISTS:

# reading from file
while ( <> ) {
    push @LoL, [ split ];
}

# calling a function 
for $i ( 1 .. 10 ) {
    $LoL[$i] = [ somefunc($i) ];
}

# using temp vars
for $i ( 1 .. 10 ) {
    @tmp = somefunc($i);
    $LoL[$i] = [ @tmp ];
}

# add to an existing row
push @{ $LoL[0] }, "wilma", "betty";

Access and Printing of a LIST OF LISTS:

# one element
$LoL[0][0] = "Fred";

# another element
$LoL[1][1] =~ s/(\w)/\u$1/;

# print the whole thing with refs
for $aref ( @LoL ) {
    print "\t [ @$aref ],\n";
}

# print the whole thing with indices
for $i ( 0 .. $#LoL ) {
    print "\t [ @{$LoL[$i]} ],\n";
}

# print the whole thing one at a time
for $i ( 0 .. $#LoL ) {
    for $j ( 0 .. $#{$LoL[$i]} ) {
	print "elt $i $j is $LoL[$i][$j]\n";
    }
}