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-rw-r--r--net/ricketyspace/sicp/two/fortytwo.scm8
1 files changed, 7 insertions, 1 deletions
diff --git a/net/ricketyspace/sicp/two/fortytwo.scm b/net/ricketyspace/sicp/two/fortytwo.scm
index 7ccf00e..e284591 100644
--- a/net/ricketyspace/sicp/two/fortytwo.scm
+++ b/net/ricketyspace/sicp/two/fortytwo.scm
@@ -3,7 +3,8 @@
;;;;
(define-module (net ricketyspace sicp two fortytwo)
- #:export (safe?))
+ #:export (safe?
+ adjoin-position))
(define (accumulate op initial sequence)
(if (null? sequence)
@@ -52,3 +53,8 @@
positions)))
(if (null? in-same-diag) #f #t)))
(not (or (same-row?) (same-diagonal?))))
+
+
+(define (adjoin-position new-row k rest-of-queens)
+ (let ((queen-at-k (cons new-row k)))
+ (append rest-of-queens (list queen-at-k))))