1 files changed, 9 insertions, 0 deletions
diff --git a/rkt/double.rkt b/rkt/double.rkt
new file mode 100644
index 0000000..3ef0755
--- /dev/null
+++ b/rkt/double.rkt
@@ -0,0 +1,9 @@
+#lang racket
+
+(define (double v)
+  ((if (string? v) string-append +) v v))
+
+(string-append "ba"
+               (double "na"))
+
+(double 21)
\ No newline at end of file