Initial data commit

Task/Execute-a-Markov-algorithm/Scheme/execute-a-markov-algorithm.ss

@@ -0,0 +1,47 @@
+(define split-into-lines
+  (lambda (str)
+    (let loop ((index 0)
+               (result '()))
+      (let ((next-index (string-index str #\newline index)))
+        (if next-index
+            (loop (+ next-index 1)
+                  (cons (substring str index next-index) result))
+            (reverse (cons (substring str index) result)))))))
+
+(define parse-rules
+  (lambda (str)
+    (let loop ((rules (split-into-lines str))
+               (result '()))
+      (if (null? rules)
+          (reverse result)
+          (let ((rule (car rules)))
+            (loop (cdr rules)
+                  (if (or (string=? rule "")
+                          (eq? (string-ref rule 0) #\#))
+                      result
+                      (cons
+                       (let ((index (string-contains rule "->" 1)))
+                         (list (string-trim-right (substring rule 0 index))
+                               (string-trim (substring rule (+ index 2)))))
+                       result))))))))
+
+
+(define apply-rules
+  (lambda (str rules)
+    (let loop ((remaining rules)
+               (result str))
+      (if (null? remaining)
+          result
+          (let* ((rule (car remaining))
+                 (pattern (car rule))
+                 (replacement (cadr rule))
+                 (start (string-contains result pattern)))
+            (if start
+                (if (eq? #\. (string-ref replacement 0))
+                    (string-replace result replacement start
+                                    (+ start (string-length pattern)) 1)
+                    (apply-rules
+                     (string-replace result replacement start
+                                     (+ start (string-length pattern)))
+                     rules))
+                (loop (cdr remaining) result)))))))