minor tweaks

contrib/math/polynomials.factor

@@ -110,8 +110,8 @@ IN: math-contrib
 
 : pdiff ( p -- p' )
     #! Polynomial derivative.
-    dup empty? [ [ length ] keep v* 1 swap tail ] unless ;
+    dup length v* { 0 } ?head drop ;
 
-: polyval ( x p -- p[x] )
+: polyval ( p x -- p[x] )
     #! Evaluate a polynomial.
-    [ powers ] keep v. ;
+    >r dup length r> powers v. ;

contrib/math/utils.factor

@@ -26,9 +26,9 @@ USING: errors kernel sequences math sequences-internals namespaces arrays ;
         -rot (^mod)
     ] if ; foldable
 
-: powers ( x n -- { 1 x x^2 x^3 ... } )
+: powers ( n x -- { 1 x x^2 x^3 ... } )
     #! Output sequence has n elements.
-    1 swap [ drop [ dupd * ] keep ] map 2nip ;
+    <array> 1 [ * ] accumulate ;
 
 : ** ( u v -- u*v' ) conjugate * ; inline