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diff --git a/net/ricketyspace/sicp/one/twentynine.scm b/net/ricketyspace/sicp/one/twentynine.scm
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+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one twentynine)
+  #:export (simpsons))
+
+(define (sum term a next b)
+  (if (> a b)
+      0
+      (+ (term a)
+         (sum term (next a) next b))))
+
+(define (simpsons f a b n)
+  (let* ((h (/ (- b a) (* 1.0 n)))
+         (y (lambda (k) (+ a (* k h))))
+         (ce (lambda (k) ;coefficient
+               (cond ((or (= k 0) (= k n)) 1)
+                     ((even? k) 2)
+                     (else 4))))
+         (term (lambda (k)
+                 (* (ce k) (f (y k)))))
+         (next (lambda (k) (1+ k))))
+    (* (/ h 3.0)
+       (sum term 0 next n))))