Remove cache-nth word, nobody was using it and the semantics were broken

core/sequences/sequences-docs.factor

@@ -416,11 +416,6 @@ HELP: interleave
 { $description "Applies " { $snippet "quot" } " to each element in turn, also invoking " { $snippet "between" } " in-between each pair of elements." }
 { $example "USING: io sequences ;" "{ \"a\" \"b\" \"c\" } [ \"X\" write ] [ write ] interleave" "aXbXc" } ;
 
-HELP: cache-nth
-{ $values { "i" "a non-negative integer" } { "seq" "a mutable sequence" } { "quot" { $quotation "( i -- elt )" } } { "elt" object } }
-{ $description "If the sequence does not contain at least " { $snippet "i" } " elements or if the " { $snippet "i" } "th element of the sequence is " { $link f } ", calls the quotation to produce a new value, and stores it back into the sequence. Otherwise, this word outputs the " { $snippet "i" } "th element of the sequence." }
-{ $side-effects "seq" } ;
-
 HELP: index
 { $values { "obj" object } { "seq" sequence } { "n" "an index" } }
 { $description "Outputs the index of the first element in the sequence equal to " { $snippet "obj" } ". If no element is found, outputs " { $link f } "." } ;
@@ -1497,7 +1492,6 @@ ARTICLE: "sequences-destructive" "Destructive operations"
 "Changing elements:"
 { $subsection change-each }
 { $subsection change-nth }
-{ $subsection cache-nth }
 "Deleting elements:"
 { $subsection delete }
 { $subsection delq }

core/sequences/sequences-tests.factor

@@ -190,16 +190,6 @@ unit-test
 
 [ V{ "a" "b" } V{ } ] [ { "X" "a" "b" } { "X" } drop-prefix [ >vector ] bi@ ] unit-test
 
-[ 1 4 9 16 16 V{ f 1 4 9 16 } ] [
-    V{ } clone "cache-test" set
-    1 "cache-test" get [ sq ] cache-nth
-    2 "cache-test" get [ sq ] cache-nth
-    3 "cache-test" get [ sq ] cache-nth
-    4 "cache-test" get [ sq ] cache-nth
-    4 "cache-test" get [ "wrong" ] cache-nth
-    "cache-test" get
-] unit-test
-
 [ 1 ] [ 0.5 { 1 2 3 } nth ] unit-test
 
 ! Pathological case

core/sequences/sequences.factor

@@ -523,13 +523,6 @@ PRIVATE>
 : harvest ( seq -- newseq )
     [ empty? not ] filter ;
 
-: cache-nth ( i seq quot -- elt )
-    2over ?nth dup [
-        [ 3drop ] dip
-    ] [
-        drop swap [ over [ call dup ] dip ] dip set-nth
-    ] if ; inline
-
 : mismatch ( seq1 seq2 -- i )
     [ min-length ] 2keep
     [ 2nth-unsafe = not ] 2curry