sequences.extras: adding join-with.

extra/sequences/extras/extras-tests.factor

@@ -262,3 +262,7 @@ tools.test vectors vocabs ;
 { { 4 5 6 7 } } [ 8 <iota> [ 4 < ] drop-while >array ] unit-test
 { { 15 16 } } [ { 15 16 } [ 4 < ] drop-while >array ] unit-test
 { { } } [ 3 <iota> [ 4 < ] drop-while >array ] unit-test
+
+{ { } } [ { } ", " join-with ] unit-test
+{ { 1 } } [ { 1 } ", " join-with ] unit-test
+{ { 1 ", " 2 } } [ { 1 2 } ", " join-with ] unit-test

extra/sequences/extras/extras.factor

@@ -625,3 +625,8 @@ PRIVATE>
 : drop-while ( ... seq quot: ( ... elt -- ... ? ) -- tail-slice )
     [ '[ @ not ] find drop ] 2keep drop swap
     [ dup length ] unless* tail-slice ; inline
+
+: join-with ( seq glue -- newseq )
+    V{ } clone [
+        [ '[ _ _ push ] ] [ '[ _ push ] ] bi interleave
+    ] keep { } like ;