one/twelve.scm: add printing functions

They work only when all values of the triangle are single digit.

1 files changed, 17 insertions, 1 deletions

diff --git a/one/twelve.scm b/one/twelve.scm
index 39c3d8b..1e201dc 100644
--- a/one/twelve.scm
+++ b/one/twelve.scm
@@ -8,7 +8,9 @@
   #:export (compute-triangle
             compute-line
             display-line
-            value-at))
+            value-at
+            print-triangle
+            print-line))
 
 (define (compute-triangle n)
   (cond ((= n 1) (list (compute-line n 1)))
@@ -28,3 +30,17 @@
         (else (+
                (value-at (- line 1) (- pos 1))
                (value-at (- line 1) pos)))))
+
+;;;; printing
+
+(define (print-triangle tl level)
+  (cond ((= (length tl) 0) #t)
+        (else
+         (print-triangle (cdr tl) (+ 1 level))
+         (print-line (car tl) level))))
+
+(define (print-line l level)
+  (let* ((l (map number->string l))
+        (spaces (string-join (make-list level " ") ""))
+        (line (string-append spaces (string-join l))))
+    (format #t "~a\n" line)))