#!/usr/bin/perl
use rel;

declare {

double => rel {
	alias my ($two, $one) = @_;
	oi => det { $two = $one * 2; },
	io => det { $one = $two / 2; },
},

add => rel {
	alias my ($sum, $a, $b) = @_;
	oii => det { $sum = $a + $b; },
	ioi => det { $a = $sum - $b; },
	iio => det { $b = $sum - $a; },
},

mul => rel {
	alias my ($prod, $a, $b) = @_;
	oii => det { $prod = $a * $b; },
	ioi => det { $a = $prod / $b; },
	iio => det { $b = $prod / $a; },
},

square => rel {
	alias my ($square, $root) = @_;
	oi => det { $square = $root * $root; },
	io => multi {
		if ($square > 0) {
			option { $root = sqrt($square) };
			option { $root = -$root };
		} elsif ($square == 0) {
			option { $root = 0 };
		}
	},
},

split_join => rel {
	alias my ($list, $delim, $string) = @_;
	oii => det { @$list = split /\Q$delim\E/, $string, -1; },
	iio => det { $string = join $delim, @$list; },
	ioi => multi {
		# this mode is bogus / useless, but anyway it's a demo!
		my $split_len = 0; $split_len += length($_) for @$list;
		my $delim_len = (length($string) - $split_len) / (@$list-1);
		if ($delim_len >= 0 && is_int($delim_len)) {
			# TODO check all delimiters are the same?
			# but who cares, this is bogus anyway!
			option { $delim = substr $string, length($list->[0]//''), $delim_len; }
		}
	},
},

};


graph {
	our ($x, $y) = (7, undef);
	double($x, $y);
	solve {
		say $y;
	} $y;
	say defined $y ? "defined: $y" : "undef";

	($x, $y) = (undef, 2);
	solve {
		say $x;
	} $x;
};
say;

graph {
	my ($a, $b) = (9, undef);
	square($a, $b);
	solve_all {
		say $a, $b;
	};
};
say;

graph {
	my ($a, $b, $c, $d, $e) = (81, undef, undef, 16, undef);
	square($a, $b);
	add($c, $b, $d);
	square($c, $e);
	solve {
		say $a, $b, $c, $d, $e;
	} $e;
};
say;

graph {
	my ($list, $delim, $string) = (undef, " ", "hello world this is nice");
	split_join($list, $delim, $string);
	solve {
		say $_ for @$list;
	} $list;
	$list = [qw(wonderful library this is)]; $delim = '//'; $string = undef;
	solve_all {
		say $string;
		keep;
	};
	$delim = undef;
	solve_all {
		say $delim;
		stop;
	};
	$delim = '/';
	$list = undef;
	solve_all { say @$list; keep };
	$delim = ' AND '; undef $string;
	solve_all { say $string };
};
say;
 
# TODO support tables / enumerated relations, and efficient joining / solving of those


# TODO something so it can propogate changes: to values, lists, e.g. splice,
# set value..., strings e.g. substr $foo, 5, 10, $bar, hashes / objects...