beoliver

//
//  tries.c
//  chitchat
//
//  Created by Ben Oliver on 06/11/15.
//  Copyright © 2015 Ben Oliver. All rights reserved.
//

// assume that we allow 8 char sequences from an alphabet of 26 characters
// there are 26 ^ 8 possible sequences 208,827,064,576

beoliver

class Memoize(object):

    def __init__(self, f):
        self.f = f
        self.computed = {}

    def __call__(self, *args):
        xs = self.computed.get(args)
        if xs : 
            return xs

beoliver

def memoize(f):
    computed = {}
    def memoized(*args):
        xs = computed.get(args)
        if xs : 
            return xs
        else : 
            value = f(*args)

beoliver

import java.util.Random;

/**
 * Created by boliver on 03/06/15.
 */
public class Main {

    public static void main(String args[]) {

        Container value = new Container();

beoliver

(define (make-balance)
  (let ((balance 0))
    (define add-method
      (lambda (value) (set! balance (+ balance value))))
    (define get-method
      (lambda () balance))
    (define sub-method
      (lambda (value) 
        (if (<= value balance)
            (set! balance (- balance value))

beoliver

(define (make-counter-1)
  (let ((counter 0))
    (lambda ()      
      (set! counter (+ counter 1))
      counter)))

(define (make-counter-2)
  (define counter 0)
    (lambda ()      
      (set! counter (+ counter 1))

beoliver

> (define (foo)
    (let ((xs '(1 2 3)))
      (define (f)
	(set! xs 0))
      (f)
      xs))

> (foo)
0

beoliver

;; delay and force are defined in r5rs,
;; but if we were defining them for ourselves


(define-syntax my-delay
  (syntax-rules ()
    ((_ expr) 
      (lambda () expr))))

(define (my-force expr)

beoliver

(require r5rs)

(define xs '(1 2 3 4 5)) ;; xs is a list of numbers
xs
(set! xs "a list of numbers") ;; xs is now "a list of numbers"
xs

(define (update-1 arg)
  (set! arg "this has only changed the value of 'arg' within 'update-1'")
  arg)

beoliver

(require r5rs)

(define (set-nth! n xs x)
  (cond ((null? xs) (error "index out of bounds"))
        ((eq? n 0)  (set-car! xs x))
        (#t         (set-nth! (- n 1) (cdr xs) x))))