 
 ARTICLE: "sequences-f" "The f object as a sequence"
 "The " { $link f } " object supports the sequence protocol in a trivial way. It responds with a length of zero and throws an out of bounds error when an attempt is made to access elements." ;
+
+ARTICLE: "sequences-combinator-implementation" "Implementing sequence combinators"
+"Creating a new sequence unconditionally:"
+{ $subsections
+    accumulator
+    accumulator-for
+}
+"Creating a new sequence conditionally:"
+{ $subsections
+    pusher
+    pusher-for
+    2pusher
+} ;
 
 ARTICLE: "sequences" "Sequence operations"
 "A " { $emphasis "sequence" } " is a finite, linearly-ordered collection of elements. Words for working with sequences are in the " { $vocab-link "sequences" } " vocabulary."

           "10 [ even? ] pusher [ each ] dip ."
           "V{ 0 2 4 6 8 }"
}
{ $notes "Used to implement the " { $link filter } " word." } ;

HELP: trim-head
{ $values

"Using sequences for control flow:"
{ $subsections "sequences-if" }
"For inner loops:"
{ $subsections "sequences-unsafe" }
"Implemeting sequence combinators:"
{ $subsections "sequences-combinator-implementation" } ;

ABOUT: "sequences"
