adding lisp-interpreter

lisp-interpreter/tests/benchmarks/palindrome.scm

@@ -0,0 +1,34 @@
+; Find the largest palindrome made from the product of two 3-digit numbers.
+
+; could be 6 digits
+;   10^3 = 1,000 possible palindromes
+; or 5 digits
+;   10^3 = 1,000 possible palindromes
+
+; 2,000 total
+
+(define (palindrome? n)
+  (define (check i str)
+    (if (> (* i 2) (string-length str))
+      #t
+      (if (eq? (string-ref str i) 
+             (string-ref str (- (string-length str) (+ i 1))))
+        (check (+ i 1) str)
+        #f)))
+  (check 0 (number->string n)))
+
+(define nums '())
+  
+
+(do ((i 100 (+ i 1)))
+  ((> i 999) 'done)
+  (do ((j 100 (+ j 1)))
+    ((> j 999) 'done)
+    (let ((n (* i j)))
+      (if (>= n 100000)
+        (if (palindrome? n)
+             (push n nums)
+          )))))
+                            
+(display (reduce max 0 nums))
+