automatthew-functor

Functor provides pattern-based function and method dispatch for Ruby. To use it in a class:

class Repeater attr_accessor :times include Functor::Method functor( :repeat, Integer ) { |x| x * @times } functor( :repeat, String ) { |s| [].fill( s, 0..@times ).join(' ') } end

r = Repeater.new r.times = 5 r.repeat( 5 ) # => 25 r.repeat( "-" ) # => "- - - - -" r.repeat( 7.3 ) # => RuntimeError!

Warning: This defines a class instance variable @functors behind the scenes as a side-effect. Also, functors won't inherit properly at this point.

You can also define Functor objects directly:

fib = Functor.new do given( 0 ) { 0 } given( 1 ) { 1 } given( Integer ) { |n| self.call( n - 1 ) + self.call( n - 2 ) } end

You can use functors directly with functions taking a block like this:

[ *0..10 ].map( &fib ) # => [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]

You can explicitly bind self using #bind:

fun.bind( obj )

which is actually how the method dispatch is implemented.

Arguments are matched first using === and then ==, so anything that supports these methods can be matched against.