#!/usr/bin/ruby
#
## https://rosettacode.org/wiki/Dinesman%27s_multiple-dwelling_problem
#
func solve(n, pred) {
    gather {
        n.permutations { |*candidate|
            if (pred.all { |p| p(candidate) }) {
                take(candidate)
            }
        }
    }
}
var predicates = [
    ->(s) { last(s) != "Baker" },
    ->(s) { first(s) != "Cooper" },
    ->(s) { (first(s) != "Fletcher") && (last(s) != "Fletcher") },
    ->(s) { index(s, "Miller") > index(s, "Cooper") },
    ->(s) { abs(index(s, "Smith")  - index(s, "Fletcher")) != 1 },
    ->(s) { abs(index(s, "Cooper") - index(s, "Fletcher")) != 1 },
]
var Names = ["Baker", "Cooper", "Fletcher", "Miller", "Smith"]
var solutions = solve(Names, predicates)
solutions.each { .join(', ').say }
assert_eq(solutions, [["Smith", "Cooper", "Baker", "Fletcher", "Miller"]])