Add 1.30

sicp-ex-1.30.rkt

@@ -0,0 +1,11 @@
+#! /usr/bin/racket
+#lang racket/base
+
+(define (sum term a next b)
+  (define (iter a result)
+    (if (> a b)
+      result
+      (iter (next a) (+ (term a) result))))
+  (iter a 0))
+
+(sum (lambda (x) x) 0 (lambda (x) (+ x 1)) 3)