>>>>> "GJ" == Greg J <greg.jar...@gmail.com> writes:
GJ> Hi everyone,
GJ> I am new to Perl and I am having some trouble working with hashes of
hashes.
GJ> I am trying to write a simple Markov Chain text generator and thought
GJ> it might be a good idea to keep track of state transitions in a hash.
GJ> Here is some of the code I have..
GJ> ====================================
GJ> use Data::Dumper;
GJ> my %StateTable = ();
GJ> sub InsertWord
GJ> {
GJ> my( $state, $next ) = shift @_;
that is very wrong. either use shift to get one arg or assign @_ to a
list to get all of them. you used both styles so $next is never set to
anything (stays undef).
GJ> if( $StateTable{$state} )
GJ> {
GJ> if( $StateTable{$state}{$next} )
GJ> {
GJ> $StateTable{$state}{$next}++;
GJ> }else{
GJ> $StateTable{$state} = { $next => 1 };
GJ> }
you don't need the if/else as ++ will work on an undef entry and set it
to 1. it won't even trigger a warning as this is a common and useful
idiom.
GJ> }else{
GJ> $StateTable{$state} = { $next => 1 };
and you can also dispense with that if/else. just use ||= which won't
assign if it already has a true value and refs are always true. this
should replace all the above code (untested):
$StateTable{$state} ||= { $next => 0 };
$StateTable{$state}{$next}++;
note that i set the value to 0 so the ++ will set it to 1.
for more on hashes of hashes read perldoc perlreftut, perllol and
perldsc.
uri
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