This module implements the cell datatype as a record. It can be converted to a function, closed over some state. If this function is called without arguments, it returns the state, with one argument, it changes state.
cells[procedure] (cells [sym])
documentation procedure: Without an argument shows the list of exported symbols, with a symbol argument shows the signature of this symbol.
cell[procedure] (cell arg)
Creates and initializes a cell.
cell?[procedure] (cell? xpr)
Does xpr evaluate to a cell?
cell-of?[procedure] (cell-of? type?)
returns a predicate, which checks, if its only argument is a cell which stores an item of type?
cell-ref[procedure] (cell-ref cl)
accessor: returns the content of cell cl.
cell-set![procedure] (cell-set! cl val)
mutator: changes the content of cell cl to val.
cell->closure[procedure] (cell->closure cl)
transforms its cell argument into a closure
(use cells) (define cl (cell 5)) (cell? cl) ; -> #t (cell? 5) ; -> #f ((cell-of? number?) cl) ; -> #t ((cell-of? list?) cl) ; -> #f (cell-ref cl) ; -> 5 (cell-set! cl 50) (cell-ref cl) ; -> 50 (cell-set! cl 500) (cell-ref cl) ; -> 500 (define cc (cell->closure cl)) (cc) ; -> 500 (cc 5) (cc) ; -> 5 ;;; implementing a stack without any error checking (define (push st% val) (st% (cons val (st%)))) (define (top st%) (car (st%))) (define (pop st%) (st% (cdr (st%)))) (define stack (cell '())) (cell? stack) ; -> #t ((cell-of? list?) stack) ; -> #t ((cell-of? number?) stack) ; -> #f (define stack% (cell->closure stack)) (null? (stack%)) ; -> #t (push stack% 5) (push stack% 50) (push stack% 500) (top stack%) ; -> 500 (pop stack%) (top stack%) ; -> 50 (pop stack%) (top stack%) ; -> 5)
Jul 30, 2014
Copyright (c) 2011-2014, Juergen Lorenz All rights reserved.
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- cells as records, cell->closure added
- compound-test added
- added cells, cell-ref and cell-set!
- initial import