Add (net ricketyspace sicp two thirtynine).

* net/ricketyspace/sicp/two/thirtynine.scm: New file.

1 files changed, 22 insertions, 0 deletions

diff --git a/net/ricketyspace/sicp/two/thirtynine.scm b/net/ricketyspace/sicp/two/thirtynine.scm
new file mode 100644
index 0000000..8c05587
--- /dev/null
+++ b/net/ricketyspace/sicp/two/thirtynine.scm
@@ -0,0 +1,22 @@
+;;;; License: CC0-1.0
+
+(define-module (net ricketyspace sicp two thirtynine)
+  #:use-module (net ricketyspace sicp two thirtyeight)
+  #:export (reverse-fr
+            reverse-fl))
+
+(define (reverse-fr sequence)
+  (fold-right (lambda (x y) (append y (list x))) '() sequence))
+
+(define (reverse-fl sequence)
+  (fold-left (lambda (x y) (append (list y) x)) '() sequence))
+
+;;;
+;;; Guile REPL
+;;;
+;;; scheme@(guile-user)> ,re (net ricketyspace sicp two thirtynine)
+;;; scheme@(guile-user)> (reverse-fr '(1 2 3 4 5 6))
+;;; $8 = (6 5 4 3 2 1)
+;;; scheme@(guile-user)> (reverse-fl '(1 2 3 4 5 6))
+;;; $9 = (6 5 4 3 2 1)
+;;;