use concat instead of join.

basis/alien/prettyprint/prettyprint.factor

@@ -35,7 +35,7 @@ M: array c-type-string
     unclip
     [ [ unparse "[" "]" surround ] map ]
     [ c-type-string ] bi*
-    prefix "" join ;
+    prefix concat ;
 PRIVATE>
 
 : pprint-c-type ( c-type -- )

basis/byte-arrays/hex/hex.factor

@@ -7,8 +7,8 @@ IN: byte-arrays.hex
 ERROR: odd-length-hex-string string ;
 
 SYNTAX: HEX{
-    "}" parse-tokens "" join
+    "}" parse-tokens concat
     [ blank? not ] filter
     dup length even? [ odd-length-hex-string ] unless
-    2 group [ hex> ] B{ } map-as
+    2 <groups> [ hex> ] B{ } map-as
     suffix! ;

basis/ui/gestures/gestures.factor

@@ -326,10 +326,10 @@ M: macosx modifiers>string
             { S+ [ "\u0021e7" ] }
             { C+ [ "\u002303" ] }
         } case
-    ] map "" join ;
+    ] map concat ;
 
 M: object modifiers>string
-    [ name>> ] map "" join ;
+    [ name>> ] map concat ;
 
 HOOK: keysym>string os ( keysym -- string )
 

basis/xml/writer/writer.factor

@@ -19,7 +19,7 @@ SYMBOL: indentation
 
 : indent-string ( -- string )
     xml-pprint? get
-    [ indentation get indenter get <repetition> "" join ]
+    [ indentation get indenter get <repetition> concat ]
     [ "" ] if ;
 
 : ?indent ( -- )

core/generic/single/single.factor

@@ -161,7 +161,7 @@ M: tag-dispatch-engine compile-engine
 
 : build-fast-hash ( methods -- buckets )
     >alist V{ } clone [ hashcode 1array ] distribute-buckets
-    [ compile-engines* >alist { } join ] map ;
+    [ compile-engines* >alist concat ] map ;
 
 M: echelon-dispatch-engine compile-engine
     dup n>> 0 = [

extra/asn1/asn1.factor

@@ -215,7 +215,7 @@ M: string >ber ( str -- byte-array )
 
 : >ber-seq-internal ( array code -- byte-array )
     1array "C" pack-native swap dup length >ber-length-encoding
-    swapd append swap [ number>string ] map "" join >array append ;
+    swapd append swap [ number>string ] map { } concat-as append ;
 
 M: array >ber ( array -- byte-array )
     0x30 >ber-seq-internal ;