new polyval

contrib/math/polynomials.factor

@@ -112,7 +112,6 @@ IN: math-contrib
     #! Polynomial derivative.
     dup empty? [ [ length ] keep v* 1 swap tail ] unless ;
 
-: polyval ( x p -- n )
-    #! evaluate polynomial in a straightforward way
-    ptrim dup length 1 swap <range> [ pick swap ^ ] map 1 rot cut swapd v. swap pop + nip ;
-
+: polyval ( x p -- p[x] )
+    #! Evaluate a polynomial.
+    [ powers ] keep v. ;

contrib/math/utils.factor

@@ -26,6 +26,10 @@ USING: errors kernel sequences math sequences-internals namespaces arrays ;
         -rot (^mod)
     ] if ; foldable
 
+: powers ( x n -- { 1 x x^2 x^3 ... } )
+    #! Output sequence has n elements.
+    1 swap [ drop [ dupd * ] keep ] map 2nip ;
+
 : ** ( u v -- u*v' ) conjugate * ; inline
 
 : c. ( v v -- x )