2016 Update

Task/Loops-For-with-a-specified-step/Scheme/loops-for-with-a-specified-step-1.ss

@@ -0,0 +1,4 @@
+(do ((i 2 (+ i 2)))  ; list of variables, initials and steps -- you can iterate over several at once
+  ((>= i 9))         ; exit condition
+  (display i)        ; body
+  (newline))

Task/Loops-For-with-a-specified-step/Scheme/loops-for-with-a-specified-step-2.ss

@@ -0,0 +1,5 @@
+(let loop ((i 2))            ; function name, parameters and starting values
+  (cond ((< i 9)
+         (display i)
+         (newline)
+         (loop (+ i 2))))))  ; tail-recursive call, won't create a new stack frame

Task/Loops-For-with-a-specified-step/Scheme/loops-for-with-a-specified-step-4.ss

@@ -0,0 +1,11 @@
+(define-syntax for-loop
+  (syntax-rules ()
+    ((for-loop index start end step body ...)
+     (let ((evaluated-end end) (evaluated-step step))
+       (let loop ((i start))
+         (if (< i evaluated-end)
+           ((lambda (index) body ... (loop (+ i evaluated-step))) i)))))))
+
+(for-loop i 2 9 2
+  (display i)
+  (newline))