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Clarify functional data structures.

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Note that `set-add' is functional, clarify immutable hashes, add mutable
hash examples to contrast.
This commit is contained in:
Eli Barzilay 2013-07-16 01:55:29 -04:00
parent 5d952fb6da
commit 6af5c957d0
1 changed files with 18 additions and 7 deletions
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@ -147,10 +147,11 @@ my-pet ; => #<dog>
;;; Sets ;;; Sets
;; create a set from a list ;; Create a set from a list
(list->set '(1 2 3 1 2 3 3 2 1 3 2 1)) ; => (set 1 2 3) (list->set '(1 2 3 1 2 3 3 2 1 3 2 1)) ; => (set 1 2 3)
;; Add a member with `set-add' ;; Add a member with `set-add'
;; (Functional: returns the extended set rather than mutate the input)
(set-add (set 1 2 3) 4) ; => (set 1 2 3 4) (set-add (set 1 2 3) 4) ; => (set 1 2 3 4)
;; Remove one with `set-remove' ;; Remove one with `set-remove'
@ -162,7 +163,7 @@ my-pet ; => #<dog>
;;; Hashes ;;; Hashes
;; Create an immutable hash table (There are also mutables ones) ;; Create an immutable hash table (mutable example below)
(define m (hash 'a 1 'b 2 'c 3)) (define m (hash 'a 1 'b 2 'c 3))
;; Retrieve a value ;; Retrieve a value
@ -174,16 +175,26 @@ my-pet ; => #<dog>
;; You can provide a default value for missing keys ;; You can provide a default value for missing keys
(hash-ref m 'd 0) ; => 0 (hash-ref m 'd 0) ; => 0
;; Use `hash-set' to extend a hash table ;; Use `hash-set' to extend an immutable hash table
;; (Returns the extended hash instdead of mutating it)
(define m2 (hash-set m 'd 4)) (define m2 (hash-set m 'd 4))
m2 ; => '#hash((b . 2) (a . 1) (d . 4) (c . 3)) m2 ; => '#hash((b . 2) (a . 1) (d . 4) (c . 3))
;; Remember, these hashes are immutable! ;; Remember, these hashes are immutable!
m ; => '#hash((b . 2) (a . 1) (c . 3)) m ; => '#hash((b . 2) (a . 1) (c . 3)) <-- no `d'
;; Use `hash-remove' to remove keys ;; Use `hash-remove' to remove keys (functional too)
(hash-remove m 'a) ; => '#hash((b . 2) (c . 3)) (hash-remove m 'a) ; => '#hash((b . 2) (c . 3))
;; Create an empty mutable hash table and manipulate it
(define m3 (make-hash))
(hash-set! m3 'a 1)
(hash-set! m3 'b 2)
(hash-set! m3 'c 3)
(hash-ref m3 'a) ; => 1
(hash-ref m3 'd 0) ; => 0
(hash-remove! m3 'a)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 3. Functions ;; 3. Functions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;