Added a temporary file

Author: justinethier

erato.scm

@@ -0,0 +1,57 @@
+;; JAE - a temporary file used for testing, remove this down the road
+
+ ;; erato.scm -- sieve of Eratosthenes
+
+ ;; execution timings on a 1.9 GHz Intel Core2 + Win7-32
+
+ ;; all primes                < 10^3  < 10^4  < 10^5  < 10^6
+
+ ;; interpreter
+
+ ;; petite (chez scheme) 8.4   0 sec   0 sec   2 sec   2 min
+ ;; PLT-r5rs (racket) 5.3.6    0 sec   0 sec   2 sec   4 min
+ ;; pi (rhizome/pi) 0.57       0 sec   0 sec   2 sec   6 min
+ ;; gsi (gambit) 4.7.0         0 sec   0 sec   4 sec  13 min
+ ;; csi (chicken) 4.8.0.5      0 sec   0 sec  10 sec  18 min
+ ;; scheme 48 1.9              0 sec   0 sec  10 sec     n/a
+
+ ;; notes
+ ;; 1. most of these interpreters come with compilers. i have
+ ;; not measured execution timings for compiled code.
+ ;; 2. this is only a single application. execution timings 
+ ;; vary with application type and complexity of control
+ ;; structures.
+ ;; 3. rhizome/pi is my favorite interpreter.
+(define (append . lst)
+  (define append-2
+          (lambda (inlist alist) 
+                  (foldr (lambda (ap in) (cons ap in)) alist inlist)))
+  (if (null? lst)
+      lst
+      (if (null? (cdr lst))
+          (car lst)
+          (foldl (lambda (a b) (append-2 b a)) (car lst) (cdr lst)))))
+
+ (define (primes<2n n)
+    (erato 2 (* n 2) (list)))
+
+ (define (erato n z primes)
+
+    (define (sieve s)
+       (define ok #f)
+       (if (null? s) 
+        (set! ok #t)
+        (if (< n (* (car s) (car s))) (set! ok #t))) ; prime!
+       ;(if (or (null? s)                  ; prime
+       ;        (< n (* (car s) (car s)))) ; prime!
+       (if ok
+           (erato (+ n 1) z (append primes (list n)))
+           (if (zero? (modulo n (car s))) ; composite
+               (erato (+ n 1) z primes)
+               (sieve (cdr s)))))
+
+    (if (< n z)
+        (sieve primes)
+        primes))
+
+((lambda () (primes<2n 1000) 1))