functional

A functional programming library including a lazy list implementation and some of the most usual functions.

import FP "github.com/tcard/functional"

Installing

go get github.com/tcard/functional

Tested on Go 1.

Examples

The Fibonacci sequence, infinite stream:

var fibo *FP.Thunk
fibo = FP.Link(1, FP.DelayedLink(1, func() *FP.Thunk {
	return FP.MapN(func(xs ...FP.I) FP.I {
		ret := 0
		for _, v := range xs {
			ret += v.(int)
		}
		return ret
	}, fibo, fibo.Tail())
}))

Which is an uglier, slower version of the famous Lisp-like:

(define fibo
	(cons 1
		(cons 1
			(map + fibo (cdr fibo)))))		

For showing some "real" utility, this would retrieve the third page of a blog:

var posts *FP.Thunk	= ...
page := 3
postsPerPage := 10
_ = posts.Drop((page - 1) * postsPerPage).Take(postsPerPage).Map(func (post FP.I) FP.I {
	blog.showPost(post.(Post))
	return post
})

See documentation and tests for detailed usage.

To Do

• Better memoization.
• Ability to skip lists and work directly with slices, although lack of generics would make it clumsy anyway.
• Some optimizations.