Move conjoin-at from compiler.cfg.liveness to sets

basis/compiler/cfg/liveness/liveness.factor

@@ -43,9 +43,6 @@ SYMBOL: work-list
     [ nip kill-set ]
     2bi assoc-diff ;
 
-: conjoin-at ( value key assoc -- )
-    [ dupd ?set-at ] change-at ;
-
 : compute-phi-live-in ( basic-block -- phi-live-in )
     instructions>> [ ##phi? ] filter [ f ] [
         H{ } clone [

core/sets/sets-docs.factor

@@ -23,6 +23,7 @@ $nl
 "Adding elements to sets:"
 { $subsection adjoin }
 { $subsection conjoin }
+{ $subsection conjoin-at }
 { $see-also member? memq? any? all? "assocs-sets" } ;
 
 ABOUT: "sets"
@@ -54,6 +55,10 @@ HELP: conjoin
 }
 { $side-effects "assoc" } ;
 
+HELP: conjoin-at
+{ $values { "value" object } { "key" object } { "assoc" assoc } }
+{ $description "Adds " { $snippet "value" } " to the set stored at " { $snippet "key" } " of " { $snippet "assoc" } "." } ;
+
 HELP: unique
 { $values { "seq" "a sequence" } { "assoc" assoc } }
 { $description "Outputs a new assoc where the keys and values are equal." }

core/sets/sets.factor

@@ -7,6 +7,9 @@ IN: sets
 
 : conjoin ( elt assoc -- ) dupd set-at ;
 
+: conjoin-at ( value key assoc -- )
+    [ dupd ?set-at ] change-at ;
+
 : (prune) ( elt hash vec -- )
     3dup drop key? [ 3drop ] [
         [ drop conjoin ] [ nip push ] 3bi