rotate-circular word

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 } ;

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

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 ;