remove singleton? from sequences.lib

fix bootstrap error

extra/math/polynomials/polynomials.factor

@@ -22,7 +22,7 @@ PRIVATE>
 : p= ( p p -- ? ) pextend = ;
 
 : ptrim ( p -- p )
-    dup singleton? [ [ zero? ] right-trim ] unless ;
+    dup length 1 = [ [ zero? ] right-trim ] unless ;
 
 : 2ptrim ( p p -- p p ) [ ptrim ] bi@ ;
 : p+ ( p p -- p ) pextend v+ ;

extra/math/text/english/english.factor

@@ -79,7 +79,7 @@ SYMBOL: and-needed?
     ] if ;
 
 : recombine ( seq -- str )
-    dup singleton? [
+    dup length 1 = [
         first 3digits>text
     ] [
         dup set-conjunction "" swap

extra/random/unix/unix.factor

@@ -1,5 +1,5 @@
 USING: alien.c-types io io.files io.nonblocking kernel
-namespaces random io.encodings.binary singleton init
+namespaces random io.encodings.binary init
 accessors system ;
 IN: random.unix
 

extra/sequences/lib/lib-tests.factor

@@ -46,9 +46,6 @@ IN: sequences.lib.tests
 [ { 1 -1 5 2 4 } [ < ] monotonic-split [ >array ] map ] unit-test
 [ { { 1 1 1 1 } { 2 2 } { 3 } { 4 } { 5 } { 6 6 6 } } ]
 [ { 1 1 1 1 2 2 3 4 5 6 6 6 } [ = ] monotonic-split [ >array ] map ] unit-test
-[ f ] [ { } singleton? ] unit-test
-[ t ] [ { "asdf" } singleton? ] unit-test
-[ f ] [ { "asdf" "bsdf" } singleton? ] unit-test
 
 [ 2 ] [ V{ 10 20 30 } [ delete-random drop ] keep length ] unit-test
 [ V{ } [ delete-random drop ] keep length ] must-fail

extra/sequences/lib/lib.factor

@@ -98,9 +98,6 @@ MACRO: firstn ( n -- )
         v, [ pick ,, call [ v, ] unless ] curry 2each ,v
     ] { } make ;
 
-: singleton? ( seq -- ? )
-    length 1 = ;
-
 : delete-random ( seq -- value )
     [ length random ] keep [ nth ] 2keep delete-nth ;