From bbab60545e98bacafbaaaacff63a9584a1d7ae59 Mon Sep 17 00:00:00 2001
From: Danny Yoo <dyoo@cs.wpi.edu>
Date: Mon, 30 Jan 2012 11:21:30 -0500
Subject: [PATCH] adding gvector-remove-last!

---
 collects/data/gvector.rkt               | 17 +++++++++++++++++
 collects/data/scribblings/gvector.scrbl |  6 ++++++
 collects/tests/data/gvector.rkt         | 19 +++++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/collects/data/gvector.rkt b/collects/data/gvector.rkt
index 45a339d31d..af41b31731 100644
--- a/collects/data/gvector.rkt
+++ b/collects/data/gvector.rkt
@@ -28,6 +28,11 @@
                "")
            index)))
 
+(define (check-nonempty who n)
+  (unless (> n 0)
+    (error who "empty")))
+
+
 (define ((bad-index-error who index))
   (raise-mismatch-error who "index out of range" index))
 
@@ -67,6 +72,16 @@
            (vector-copy! v index v (add1 index) n)
            (vector-set! v (sub1 n) #f)])))
 
+(define (gvector-remove-last! gv)
+  (let ([n (gvector-n gv)]
+        [v (gvector-vec gv)])
+    (check-nonempty 'gvector-remove-last! n)
+    (define last-val (vector-ref v (sub1 n)))
+    (set-gvector-n! gv (sub1 n))
+    (vector-set! v (sub1 n) #f)
+    last-val))
+
+
 (define (gvector-count gv)
   (gvector-n gv))
 
@@ -213,6 +228,8 @@
   (->* (gvector?) () #:rest any/c any)]
  [gvector-remove!
   (-> gvector? exact-nonnegative-integer? any)]
+ [gvector-remove-last!
+  (-> gvector? any)]
  [gvector-count
   (-> gvector? any)]
  [gvector->vector
diff --git a/collects/data/scribblings/gvector.scrbl b/collects/data/scribblings/gvector.scrbl
index bfe5cf3526..4446345b99 100644
--- a/collects/data/scribblings/gvector.scrbl
+++ b/collects/data/scribblings/gvector.scrbl
@@ -83,6 +83,12 @@ down. Takes time proportional to @racket[(- (gvector-count gv)
 index)].
 }
 
+@defproc[(gvector-remove-last! [gv gvector?])
+         any/c]{
+Removes the element at the end and returns it.  Takes constant time.
+}
+
+
 @defproc[(gvector-count [gv gvector?])
          exact-nonnegative-integer?]{
 
diff --git a/collects/tests/data/gvector.rkt b/collects/tests/data/gvector.rkt
index cf60fc1302..2dc15b7e60 100644
--- a/collects/tests/data/gvector.rkt
+++ b/collects/tests/data/gvector.rkt
@@ -53,6 +53,25 @@
                (gvector->vector gv))
              '#(2 3))
 
+(test-equal? "gvector-remove-last!"
+             (let ([gv (gvector 1 2 3)])
+               (check-equal? (gvector-remove-last! gv) 3)
+               (check-equal? (gvector-remove-last! gv) 2)
+               (check-equal? (gvector-remove-last! gv) 1)
+               (gvector->vector gv))
+             '#())
+
+(test-equal? "gvector-add and gvector-remove-last!"
+             (let ([gv (gvector)])
+               (gvector-add! gv 'rock)
+               (gvector-add! gv 'paper)
+               (check-equal? (gvector-remove-last! gv) 'paper)
+               (gvector-add! gv 'scissor)
+               (check-equal? (gvector-remove-last! gv) 'scissor)
+               (check-equal? (gvector-remove-last! gv) 'rock)
+               (gvector->vector gv))
+             '#())
+
 (test-equal? "gvector-count"
              (gvector-count (gvector 1 2 3))
              3)