Data commit

Task/Hash-from-two-arrays/Scheme/hash-from-two-arrays-1.ss

@@ -0,0 +1,2 @@
+(define (lists->hash-table keys values . rest)
+  (apply alist->hash-table (map cons keys values) rest))

Task/Hash-from-two-arrays/Scheme/hash-from-two-arrays-2.ss

@@ -0,0 +1,23 @@
+;; Using SRFI-1, R6RS, or R7RS association lists.
+
+;; Because the task calls for ‘arrays’, I start with actual arrays
+;; rather than lists.
+(define array1 (vector "a" "b" "c" "d"))
+(define array2 (vector 1 2 3 4))
+
+;; Making the hash is just a simple list operation.
+(define dictionary (map cons (vector->list array1)
+                        (vector->list array2)))
+
+;; Now you can look up associations with assoc.
+(write (assoc "b" dictionary)) (newline)
+(write (assoc "d" dictionary)) (newline)
+
+;; USING CHICKEN 5 SCHEME, OUTPUT FROM EITHER
+;; ‘csc -R srfi-1 thisprog.scm && ./thisprog’
+;; OR ‘csc -R r7rs thisprog.scm && ./thisprog’,
+;; AND ALSO TESTED IN CHEZ SCHEME (R6RS):
+;;
+;; ("b" . 2)
+;; ("d" . 4)
+;;

Task/Hash-from-two-arrays/Scheme/hash-from-two-arrays-3.ss

@@ -0,0 +1,31 @@
+(import (associative-arrays))
+
+;; Because the task calls for ‘arrays’, I start with actual arrays
+;; rather than lists.
+(define array1 (vector "a" "b" "c" "d"))
+(define array2 (vector 1 2 3 4))
+
+(define (silly-hashfunc s)
+  (define h 1234)
+  (do ((i 0 (+ i 1)))
+      ((= i (string-length s)))
+    (set! h (+ h (char->integer (string-ref s i)))))
+  (sqrt (/ (* h 101) 9.80665)))
+
+;; Here is the making of the associative array:
+(define dictionary (assoc-array silly-hashfunc))
+(vector-for-each (lambda (key data)
+                   (set! dictionary
+                     (assoc-array-set dictionary key data)))
+                 array1 array2)
+
+(display "Looking up \"b\" and \"d\": ")
+(write (assoc-array-ref dictionary "b"))
+(display " ")
+(write (assoc-array-ref dictionary "d"))
+(newline)
+
+;; Output:
+;;
+;;   Looking up "b" and "d": 2 4
+;;