Implementing simple BFS in Raku for an App called Calculator-The-Game

calculator-the-game.raku

use MONKEY-SEE-NO-EVAL;

class Node {
    has $.value;
    has @.operations = [];
}

sub calculate(Int $start-value, Int $target-value, Int $max-steps, @possible-operators --> List) {
    
    my @queue = [ Node.new(value => $start-value), ];

    while @queue.shift -> $parent {
        
        for @possible-operators -> $op {

            my $child = Node.new( value      => EVAL("%s %s".sprintf($parent.value, $op)).Int,
                                  operations => $parent.operations.clone.push: $op 
                                );

            return $child.operations if $child.value == $target-value;
            
            @queue.push: $child if $child.operations.elems < $max-steps;
        }
    }
   fail "No path found from %d to %d in %d steps using operators %s.".sprintf($start-value, $target-value, $max-steps, @possible-operators.join(" | "));
}

use Test;
ok calculate(0, 2, 2, <+1 -1>) == <+1 +1>;
ok calculate(0, 5, 3, <+1 -1 +2>) == <+1 +2 +2>;
ok calculate(0, 210, 5, <~2 ~5 -5 +5>) == <~2 ~5 -5 ~5 +5>;