Racket: add readline/line edit support.

Author: kanaka

racket/readline.rkt

@@ -2,14 +2,31 @@
 
 (provide readline)
 
+(require (prefix-in readline: readline/readline))
+
 (require "types.rkt")
 
+(define history-loaded #f)
+(define HISTORY-FILE (format "~a/.mal-history" (find-system-path 'home-dir)))
+
+(define (load-history path)
+  (map 
+    (lambda (line) (readline:add-history line))
+    (string-split
+      (port->string (open-input-file path))
+      #px"\n")))
+
 (define (readline prompt)
-  (_printf "~a" prompt)
-  (let ([line (read-line (current-input-port) 'any)])
+  (when (not history-loaded)
+    (set! history-loaded #t)
+    (load-history HISTORY-FILE))
+  (let ([line (readline:readline prompt)])
     (if (eq? eof line)
       nil
-      line)))
-
-      
-
+      (begin
+        (readline:add-history line)
+        (with-output-to-file
+          HISTORY-FILE
+          (lambda () (printf "~a~n" line))
+          #:exists 'append)
+        line))))