blob: d470394b3aae3c840beb164ae39e3964016e3eac (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
|
(define-module (data stack)
#:export (pop peek push)
#:use-module (control monad)
#:use-module (control monad state))
;;; Simple stateful stack module for showing the state monad
;;; in action. These functions assume that they are in a
;;; (state list) monad. But dynamic types!
;;; TODO test these for empty stack
(define (pop)
(do st <- (get)
let top = (car st)
(put (cdr st))
(return-state top)))
(define (peek)
(do st <- (get)
(return-state (car st))))
(define (push v)
(do st <- (get)
(put (cons v st))))
|