Horner's rule for polynomial evaluation: Difference between revisions

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 =={{header|D}}==
+The poly() function of the standard library std.math module uses Horner's rule:
-<lang d>import std.stdio ;
-import std.traits ;
+<lang d>import std.stdio, std.math;
+void main() {
-CommonType!(U,V) horner(U,V)(U[] p, V x) {
-    CommonType!(U,V) acc = 0 ;
+    writeln(poly(3.0, [-19, 7, -4, 6]));
+}</lang>
-    foreach_reverse(c ; p)
+Basic implementation:
-        acc = acc * x + c ;
+<lang d>import std.stdio, std.traits;
-    return acc ;
+CommonType!(U, V) horner(U, V)(U[] p, V x) {
+    typeof(return) accumulator = 0;
+    foreach_reverse (c; p)
+        accumulator = accumulator * x + c;
+    return accumulator;
 }
 void main() {
-    auto poly = [-19, 7, -4 , 6] ;
+    auto poly = [-19, 7, -4, 6];
-    writefln("%s", poly.horner(3.0)) ;
+    writeln(poly.horner(3.0));
+}</lang>
+More functional:
+<lang d>import std.stdio, std.algorithm, std.range;
+auto horner(U, V)(U[] p, V x) {
+    return reduce!((a, b){ return a*x+b;})(cast(V)0, retro(p));
 }
-</lang>
+void main() {
+    auto poly = [-19, 7, -4, 6];
+    writeln(poly.horner(3.0));
+}</lang>
 =={{header|Erlang}}==
 <lang erlang>