new files

Task/Binary-search/Racket/binary-search.rkt

@@ -0,0 +1,13 @@
+#lang racket
+(define (binary-search x v)
+  ; loop : index index -> index or #f
+  ;   return i s.t. l<=i<h and v[i]=x
+  (define (loop l h)
+    (cond [(>= l h) #f]
+          [else (define m (quotient (+ l h) 2))
+                (define y (vector-ref v m))
+                (cond
+                  [(> y x) (loop l (- m 1))]
+                  [(< y x) (loop (+ m 1) h)]
+                  [else m])]))
+  (loop 0 (vector-length v)))