AoC 2015.1 p1+2

1 files changed, 33 insertions, 0 deletions

diff --git a/not-quite-lisp/nql.scm b/not-quite-lisp/nql.scm
new file mode 100644
index 0000000..3863f02
--- /dev/null
+++ b/not-quite-lisp/nql.scm
@@ -0,0 +1,33 @@
+(define-module (nql)
+  #:use-module (srfi srfi-13)
+  #:export (nql
+	    paren->number))
+
+
+(define (nql str count-all?)
+  "GIven string of parens STR,
+calculates '(' - ')' when
+COUNT-ALL is #t..
+
+If COUNT-ALL? is #f, returns the
+index of the first time a negative
+number is reached."
+  (let loop ((floor 0) (iteration 0) (lst (map paren->number
+					       (string->list str))))
+    (cond
+     ((and (not count-all?)
+	   (> 0 floor)) iteration)
+     ((null? lst) (and count-all? floor))
+     (#t (loop (+ (car lst) floor)
+	       (1+ iteration)
+	       (cdr lst))))))
+
+(define (paren->number char)
+  "Given a character representing a
+parenthesis, returns 1 for '(' and
+-1 for ')'.
+Returns zero for all other characters."
+  (cond
+   ((char=? char #\() 1)
+   ((char=? char #\)) -1)
+   (#t 0)))