diff --git a/extra/math/primes/factors/factors.factor b/extra/math/primes/factors/factors.factor
index 059bd67c18..80c93f2ae0 100644
--- a/extra/math/primes/factors/factors.factor
+++ b/extra/math/primes/factors/factors.factor
@@ -1,7 +1,6 @@
 ! Copyright (C) 2007 Samuel Tardieu.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: arrays kernel lists math math.primes namespaces make
-sequences ;
+USING: arrays kernel lists make math math.primes sequences ;
 IN: math.primes.factors
 
 <PRIVATE
@@ -11,14 +10,16 @@ IN: math.primes.factors
 
 : (count) ( n d -- n' )
     [ (factor) ] { } make
-    [ [ first ] keep length 2array , ] unless-empty ;
+    [ [ first ] [ length ] bi 2array , ] unless-empty ;
 
 : (unique) ( n d -- n' )
     [ (factor) ] { } make
     [ first , ] unless-empty ;
 
 : (factors) ( quot list n -- )
-    dup 1 > [ swap uncons swap >r pick call r> swap (factors) ] [ 3drop ] if ;
+    dup 1 > [
+        swap uncons swap [ pick call ] dip swap (factors)
+    ] [ 3drop ] if ;
 
 : (decompose) ( n quot -- seq )
     [ lprimes rot (factors) ] { } make ;
@@ -38,5 +39,5 @@ PRIVATE>
     dup 2 < [
         drop 0
     ] [
-        dup unique-factors dup 1 [ 1- * ] reduce swap product / *
+        dup unique-factors [ 1 [ 1- * ] reduce ] [ product ] bi / *
     ] if ; foldable
diff --git a/extra/math/primes/primes.factor b/extra/math/primes/primes.factor
index feb60c555d..820d5b6c4a 100644
--- a/extra/math/primes/primes.factor
+++ b/extra/math/primes/primes.factor
@@ -1,8 +1,7 @@
 ! Copyright (C) 2007 Samuel Tardieu.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: combinators kernel lists.lazy math math.functions math.miller-rabin
-       math.order math.primes.list math.ranges sequences sorting
-       binary-search ;
+USING: binary-search combinators kernel lists.lazy math math.functions
+    math.miller-rabin math.primes.list sequences ;
 IN: math.primes
 
 <PRIVATE
@@ -45,8 +44,7 @@ PRIVATE>
     } cond ; foldable
 
 : primes-between ( low high -- seq )
-    primes-upto
-    [ 1- next-prime ] dip
-    [ natural-search drop ] keep [ length ] keep <slice> ; foldable
+    primes-upto [ 1- next-prime ] dip
+    [ natural-search drop ] [ length ] [ ] tri <slice> ; foldable
 
 : coprime? ( a b -- ? ) gcd nip 1 = ; foldable