From 0483a5044a26ae48224116e1502c06deb30ed39c Mon Sep 17 00:00:00 2001
From: Joe Groff <arcata@gmail.com>
Date: Wed, 13 May 2009 19:31:58 -0500
Subject: [PATCH] rotate-circular word

---
 basis/circular/circular-docs.factor  | 6 ++++++
 basis/circular/circular-tests.factor | 1 +
 basis/circular/circular.factor       | 3 +++
 3 files changed, 10 insertions(+)

diff --git a/basis/circular/circular-docs.factor b/basis/circular/circular-docs.factor
index c7af57c1fe..235d5db2c7 100644
--- a/basis/circular/circular-docs.factor
+++ b/basis/circular/circular-docs.factor
@@ -43,6 +43,11 @@ HELP: push-growing-circular
      { "elt" object } { "circular" circular } }
 { $description "Pushes an element onto a " { $link growing-circular } " object." } ;
 
+HELP: rotate-circular
+{ $values
+    { "circular" circular } }
+{ $description "Advances the start index of a circular object by one." } ;
+
 ARTICLE: "circular" "Circular sequences"
 "The " { $vocab-link "circular" } " vocabulary implements the " { $link "sequence-protocol" } " to allow an arbitrary start index and wrap-around indexing." $nl
 "Creating a new circular object:"
@@ -51,6 +56,7 @@ ARTICLE: "circular" "Circular sequences"
 { $subsection <growing-circular> }
 "Changing the start index:"
 { $subsection change-circular-start }
+{ $subsection rotate-circular }
 "Pushing new elements:"
 { $subsection push-circular }
 { $subsection push-growing-circular } ;
diff --git a/basis/circular/circular-tests.factor b/basis/circular/circular-tests.factor
index 105e3790aa..3a94e14640 100644
--- a/basis/circular/circular-tests.factor
+++ b/basis/circular/circular-tests.factor
@@ -12,6 +12,7 @@ circular strings ;
 [ CHAR: e ] [ "test" <circular> 5 swap nth-unsafe ] unit-test
  
 [ [ 1 2 3 ] ] [ { 1 2 3 } <circular> [ ] like ] unit-test
+[ [ 2 3 1 ] ] [ { 1 2 3 } <circular> [ rotate-circular ] keep [ ] like ] unit-test
 [ [ 2 3 1 ] ] [ { 1 2 3 } <circular> 1 over change-circular-start [ ] like ] unit-test
 [ [ 3 1 2 ] ] [ { 1 2 3 } <circular> 1 over change-circular-start 1 over change-circular-start [ ] like ] unit-test
 [ [ 3 1 2 ] ] [ { 1 2 3 } <circular> -100 over change-circular-start [ ] like ] unit-test
diff --git a/basis/circular/circular.factor b/basis/circular/circular.factor
index 9f3a71f2a8..909b2ed713 100644
--- a/basis/circular/circular.factor
+++ b/basis/circular/circular.factor
@@ -27,6 +27,9 @@ M: circular virtual-seq seq>> ;
     #! change start to (start + n) mod length
     circular-wrap (>>start) ;
 
+: rotate-circular ( circular -- )
+    [ start>> 1 + ] keep circular-wrap (>>start) ;
+
 : push-circular ( elt circular -- )
     [ set-first ] [ 1 swap change-circular-start ] bi ;