gistfile1.js

interface Functor {
	fmap: (any) => any;
}

interface Monad extends Functor {
	bind: (any) => Monad;
}

interface MaybeMatcher {
	just: (any) => Maybe;
	nothing: () => Maybe;
}

interface Maybe extends Monad {
	fmap: (any) => any;
	bind: (any) => Maybe;
	match: (MaybeMatcher) => Maybe;
}


class Just implements Maybe {
	private value: any;
	constructor(a: any) {
		this.value = a
	}
	fmap (f: (any) => any): Just {
		return new Just(f(this.value))
	}
	bind (f: (any) => Maybe): Maybe {
		return f(this.value)
	}
	match (matcher: MaybeMatcher): Maybe {
		return matcher.just(this.value)
	}
}

class Nothing implements Maybe {
	fmap (f: (any) => any): Nothing {
		return this
	}
	bind (f: (any) => Maybe): Maybe {
		return this
	}
	match (matcher: MaybeMatcher): Maybe {
		return matcher.nothing()
	}
}

var maybe = new Just("hoge")
var matched = maybe.match({
	just: (s: any): Maybe => {
		return new Just(s + "hoge")
	},
	nothing: (): Maybe => {
		return new Just("nothing..")
	}
})

matched.fmap((s: any): any => {console.log(s)})