NAME
Game::Merrills::Error - a move the game refused, and why
VERSION
Version 0.03
SYNOPSIS
my $move = $game->move('d2-d4');
if (ref $move eq 'Game::Merrills::Error') {
$move->code; # 'not_a_move'
$move->message; # 'that is not a move'
$move->not_a_move; # 1
$move->legal; # what could be played instead
}DESCRIPTION
When a player asks for something the rules do not allow, the game does not die. It hands back one of these in place of the move, and the game is left exactly as it was.
Every refusal has one flag set, a name for the reason that code can test, and a message a person can read. The message is a sentence without its capital or its full stop, so it can be put into a longer one.
throw is the house's name for making one. It returns the object and does not die.
The reasons
- game_over
-
The game has ended.
- not_a_move
-
What was asked for could not be read as a move at all.
- men_in_hand
-
A man was moved while the side still has men to place.
- no_men_in_hand
-
A man was placed when the side has none left in hand.
- not_your_man
-
The point to move from holds no man of the side to move.
- occupied
-
The point to land on is not empty.
- not_adjacent
-
The man was moved to a point that is not next to it along a line, by a side that may not fly.
- must_remove
-
The move closes a mill and does not say which man it takes.
- nothing_to_remove
-
The move names a man to take and closes no mill.
- no_man_there
-
The point named to take from holds no enemy man.
- man_in_mill
-
The man named is in a mill, and an enemy man outside any mill could be taken instead.
- not_legal
-
The move is not legal for a reason none of the others covers.
- no_offer
-
A draw was accepted or declined that the other side had not offered.
- nothing_to_undo
-
No move has been played, so none can be taken back.
PROPERTIES
All are read only.
game_over
not_a_move
men_in_hand
no_men_in_hand
not_your_man
occupied
not_adjacent
must_remove
nothing_to_remove
no_man_there
man_in_mill
not_legal
no_offer
nothing_to_undo
One for each reason above, true on the refusal that has that reason and undefined on every other.
$error->occupied;error
Always true, so that anything a game returns can be asked whether it is one.
$error->error;message
The reason, as a sentence without its capital or full stop.
$error->message;legal
An arrayref of the Game::Merrills::Move objects that could have been played instead. Empty when the game is over.
$error->legal;METHODS
throw
Makes a refusal from a flag, with anything further to set on it. Returns it. Dies when the flag is not one of the reasons.
my $error = Game::Merrills::Error->throw('occupied', legal => $moves);flags
Every reason, as a list, in the order a refusal is searched for its code.
my @flags = Game::Merrills::Error->flags;messages
A hashref of the message for every reason, a fresh copy each time.
my $messages = Game::Merrills::Error->messages;code
The name of the reason.
$error->code; # 'occupied'stringify
The same as "message".
$error->stringify;PACKAGE VARIABLES
AUTHOR
LNATION, <email at lnation.org>
LICENSE AND COPYRIGHT
This software is Copyright (c) 2026 by LNATION.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)