Initial data commit

Task/Subtractive-generator/Racket/subtractive-generator.rkt

@@ -0,0 +1,30 @@
+#lang racket
+(define (make-initial-state a-list max-i)
+  (for/fold ((state a-list))
+            ((i (in-range (length a-list) max-i)))
+    (append state (list (- (list-ref state (- i 2)) (list-ref state (- i 1))))))) ;from the seed and 1 creates the initial state
+
+(define (shuffle a-list)
+  (for/list ((i (in-range (length a-list))))
+    (list-ref a-list (modulo (* 34 (add1 i)) 55))))  ;shuffles the state
+
+(define (advance-state state (times 1))
+  (cond ((= 0 times) state)
+        (else (advance-state
+               (cdr (append state
+                            (list (modulo (- (list-ref state 0) (list-ref state 31))
+                                          (expt 10 9)))))
+                             (sub1 times)))))  ;takes a state and the times it must be advanced, and returns the new state
+
+(define (create-substractive-generator s0)
+  (define s1 1)
+  (define first-state (make-initial-state (list s0 s1) 55))
+  (define shuffled-state (shuffle first-state))
+  (define last-state (advance-state shuffled-state 165))
+  (lambda ((m (expt 10 9)))
+    (define new-state (advance-state last-state))
+    (set! last-state new-state)
+    (modulo (car (reverse last-state)) m)))                    ;the lambda is a function with an optional argument
+                                                               ;that returns a new random number each time it's called
+(define rand (create-substractive-generator 292929))
+(build-list 3 (lambda (_) (rand)))  ;returns a list made from the 3 wanted numbers