use Number::Interval;
use strict;
use warnings;

my @x_int = (
	Number::Interval->new( Max => 1 ),
	Number::Interval->new( Min => 1, Max => 3.3 ),
	Number::Interval->new( Min => 3.3 ),
);

my @y_int = (
	Number::Interval->new( Max => 2.5 ),
	Number::Interval->new( Min => 2.5, Max => 3.5 ),
	Number::Interval->new( Min => 3.5 ),
);

my %f;
$f{0,0} = 4;
$f{1,0} = 6;
# . . .
$f{0,1} = 3;
# . . .

for (
	# x, y
	[ 0, 0 ],
	[ 2, 0 ],
	[ 0, 3 ],
)
{
	my( $x, $y ) = @$_;

	my( $xkey ) = grep { $x_int[$_]->contains($x) } 0 .. $#x_int;
	my( $ykey ) = grep { $y_int[$_]->contains($y) } 0 .. $#y_int;

	my $z = $f{$xkey,$ykey};

	print "( $x $y ) -> $z\n";
}