commit a3bdeaf28b0527317ce3dbf9ce5b8c95fa98782d
parent 8043c65788a09f6d2f4d907e138007ffb8d563c4
Author: Ed van Bruggen <edvb@uw.edu>
Date: Wed, 9 Oct 2019 23:57:55 -0700
Clean up list manipulation functions
Diffstat:
| tibs/lib.tsp | | | 49 | +++++++++++++++++++++++++------------------------ |
1 file changed, 25 insertions(+), 24 deletions(-)
diff --git a/tibs/lib.tsp b/tibs/lib.tsp
@@ -94,6 +94,12 @@
(cons (car lst) (apply list* (cdr lst)))
(car lst)))
+(define (length lst)
+ (recur f ((lst lst) (x 0))
+ (if lst
+ (f (cdr lst) (+ x 1))
+ x)))
+
(define (last lst)
(if (cdr lst)
(last (cdr lst))
@@ -105,11 +111,16 @@
(car lst)
(nth (- i 1) (cdr lst)))))
-(define (length lst)
- (recur f ((lst lst) (x 0))
- (if lst
- (f (cdr lst) (+ x 1))
- x)))
+(define (apply proc args)
+ (eval (map (lambda (x) ; prevent args from being evaluated twice
+ (list 'quote x))
+ (cons proc args))))
+
+(define (map proc lst)
+ (if lst
+ (cons (proc (car lst))
+ (map proc (cdr lst)))
+ nil))
(define (reverse l)
(recur f ((in l) (out nil))
@@ -117,25 +128,10 @@
(f (cdr in) (cons (car in) out))
out)))
-(define (apply fn args)
- (eval (map (lambda (x)
- (list 'quote x))
- (cons fn args))))
-
-(define (map fn lst)
- (if lst
- (cons (fn (car lst))
- (map fn (cdr lst)))
- nil))
-
-(define (append l1 l2)
- (cond ((nil? l1) l2)
- (else (cons (car l1) (append (cdr l1) l2)))))
-
-(define (assoc key table)
- (cond ((nil? table) nil)
- ((= key (caar table)) (car table))
- (else (assoc key (cdr table)))))
+(define (append x y)
+ (if x
+ (cons (car x) (append (cdr x) y))
+ y))
(define (zip x y)
(cond ((and (nil? x) (nil? y)) nil)
@@ -143,6 +139,11 @@
(cons (cons (car x) (car y))
(zip (cdr x) (cdr y))))))
+(define (assoc key table)
+ (cond ((nil? table) nil)
+ ((= key (caar table)) (car table))
+ (else (assoc key (cdr table)))))
+
(define (member? mem lst)
(cond ((nil? lst) nil)
((= mem (car lst)) t)
