35.12 Chain iteration thunks

Iteration thunks are procedures accepting no arguments and returning an item from a collection; when the iteration finishes: the return value is the void object. Iteration thunks can be used with the facilities of the library (vicare containers iteration-thunks) (see iteration thunks). The following syntactic bindings are exported by the library (vicare containers chains).

Function: make-chain-forwards-iteration-thunk chain

Build and return a new iteration thunk visiting the objects from chain. The iteration proceeds forwards from chain.

(import (vicare)
  (vicare containers chains)
  (vicare containers iteration-thunks))

(define (xcons a b)
  (cons b a))

(iteration-thunk-fold
    xcons
  '()
  (make-chain-forwards-iteration-thunks (chain)))
⇒ ()

(iteration-thunk-fold
    xcons
  '()
  (make-chain-forwards-iteration-thunks (chain 0 1 2 3 4 5)))
⇒ (5 4 3 2 1 0)

Function: make-chain-backwards-iteration-thunk chain

Build and return a new iteration thunk visiting the objects from chain. The iteration proceeds backwards from chain.

(import (vicare)
  (vicare containers chains)
  (vicare containers iteration-thunks))

(define (xcons a b)
  (cons b a))

(iteration-thunk-fold
    xcons
  '()
  (make-chain-backwards-iteration-thunks (chain)))
⇒ ()

(iteration-thunk-fold
    xcons
  '()
  (make-chain-backwards-iteration-thunks
     (chain-rear (chain 0 1 2 3 4 5))))
⇒ (0 1 2 3 4 5)