Add (net ricketyspace sicp two thirtysix).

1 files changed, 27 insertions, 0 deletions

diff --git a/net/ricketyspace/sicp/two/thirtysix.scm b/net/ricketyspace/sicp/two/thirtysix.scm
new file mode 100644
index 0000000..dba2635
--- /dev/null
+++ b/net/ricketyspace/sicp/two/thirtysix.scm
@@ -0,0 +1,27 @@
+;;;; License: CC0-1.0
+
+(define-module (net ricketyspace sicp two thirtysix)
+  #:export (accumulate-n))
+
+
+(define (accumulate op initial sequence)
+  (if (null? sequence)
+      initial
+      (op (car sequence)
+          (accumulate op initial (cdr sequence)))))
+
+
+(define (accumulate-n op init seqs)
+  (if (null? (car seqs))
+      '()
+      (cons (accumulate op init (map (lambda (seq) (car seq)) seqs))
+            (accumulate-n op init (map (lambda (seq) (cdr seq)) seqs)))))
+
+
+;;; Guile REPL
+;;;
+;;; scheme@(guile-user)> ,use (net ricketyspace sicp two thirtysix)
+;;; scheme@(guile-user)> (accumulate-n + 0 '((1 2 3) (4 5 6) (7 8 9) (10 11 12)))
+;;; $9 = (22 26 30)
+;;; scheme@(guile-user)> (accumulate-n + 0 '((2 4 6) (3 6 9) (4 8 12) (5 10 15) (6 12 18)))
+;;; $10 = (20 40 60)