d5

2017/d5/main.rkt

@@ -0,0 +1,25 @@
+#lang sugar/debug br/quicklang
+(require "../helper.rkt")
+
+(provide read-syntax)
+(define (read-syntax path port)
+  (strip-context #`(module mod "main.rkt"
+                     #,@(for/list ([datum (in-port read port)])
+                          datum))))
+
+(provide (rename-out [#%mb #%module-begin]))
+(define-macro (#%mb STARS JMP ...)
+  #'(#%module-begin (escape 'STARS (list->vector '(JMP ...)))))
+
+(define (escape stars vec)
+  (let/ec exit
+    (for/fold ([pos 0])
+              ([i (in-naturals)])
+      (unless (<= 0 pos (sub1 (vector-length vec)))
+        (exit i))
+      (define jmp (vector-ref vec pos))
+      (vector-set! vec pos (if (and (eq? stars '★★) (>= jmp 3))
+                               (sub1 jmp)
+                               (add1 jmp)))
+      (+ pos jmp))))
+

2017/d5/test1.rkt

@@ -0,0 +1,6 @@
+#lang reader "main.rkt" ★
+0
+3
+0
+1
+-3

2017/d5/test2.rkt

@@ -0,0 +1,6 @@
+#lang reader "main.rkt" ★★
+0
+3
+0
+1
+-3