Update all new Tasks

Task/String-prepend/Racket/string-prepend.rkt

@@ -0,0 +1,12 @@
+;there is no built-in way to set! prepend in racket
+(define str "foo")
+(set! str (string-append "bar " str))
+(displayln str)
+
+;but you can create a quick macro to solve that problem
+(define-syntax-rule (set-prepend! str value)
+  (set! str (string-append value str)))
+
+(define macrostr " bar")
+(set-prepend! macrostr "foo")
+(displayln macrostr)