Rework most of the Rat math functions to use / to construct Rats rath…

…er than Rat.new.

This means that Rat math will automatically fall back to Num math if the intermediate values cannot be represented as Ints in Rakudo.  (Previously it would yield a cryptic error message because Rat.new insisted on Int arguments.)

src/setting/Rat.pm

@@ -55,57 +55,57 @@ class Rat {
 }
 
 multi sub infix:<+>(Rat $a, Rat $b) {
-    Rat.new($a.numerator * $b.denominator + $b.numerator * $a.denominator,
-            $a.denominator * $b.denominator );
+    ($a.numerator * $b.denominator + $b.numerator * $a.denominator)
+        / ($a.denominator * $b.denominator);
 }
 
 multi sub infix:<+>(Rat $a, Int $b) {
-    Rat.new($a.numerator + $b * $a.denominator, $a.denominator);
+    ($a.numerator + $b * $a.denominator) / $a.denominator;
 }
 
 multi sub infix:<+>(Int $a, Rat $b) {
-    Rat.new($a * $b.denominator + $b.numerator, $b.denominator);
+    ($a * $b.denominator + $b.numerator) / $b.denominator;
 }
 
 multi sub infix:<->(Rat $a, Rat $b) {
-    Rat.new($a.numerator * $b.denominator - $b.numerator * $a.denominator,
-            $a.denominator * $b.denominator );
+    ($a.numerator * $b.denominator - $b.numerator * $a.denominator)
+        / ($a.denominator * $b.denominator);
 }
 
 multi sub infix:<->(Rat $a, Int $b) {
-    Rat.new($a.numerator - $b * $a.denominator, $a.denominator);
+    ($a.numerator - $b * $a.denominator) / $a.denominator;
 }
 
 multi sub infix:<->(Int $a, Rat $b) {
-    Rat.new($a * $b.denominator - $b.numerator, $b.denominator);
+    ($a * $b.denominator - $b.numerator) / $b.denominator;
 }
 
 multi sub prefix:<->(Rat $a) {
     Rat.new(-$a.numerator, $a.denominator);
 }
 
 multi sub infix:<*>(Rat $a, Rat $b) {
-    Rat.new($a.numerator * $b.numerator, $a.denominator * $b.denominator);
+    ($a.numerator * $b.numerator) / ($a.denominator * $b.denominator);
 }
 
 multi sub infix:<*>(Rat $a, Int $b) {
-    Rat.new($a.numerator * $b, $a.denominator);
+    ($a.numerator * $b) / $a.denominator;
 }
 
 multi sub infix:<*>(Int $a, Rat $b) {
-    Rat.new($a * $b.numerator, $b.denominator);
+    ($a * $b.numerator) / $b.denominator;
 }
 
 multi sub infix:</>(Rat $a, Rat $b) {
-    Rat.new($a.numerator * $b.denominator, $a.denominator * $b.numerator);
+    ($a.numerator * $b.denominator) / ($a.denominator * $b.numerator);
 }
 
 multi sub infix:</>(Rat $a, Int $b) {
-    Rat.new($a.numerator, $a.denominator * $b);
+    $a.numerator / ($a.denominator * $b);
 }
 
 multi sub infix:</>(Int $a, Rat $b) {
-    Rat.new($b.denominator * $a, $b.numerator);
+    ($b.denominator * $a) / $b.numerator;
 }
 
 multi sub infix:</>(Int $a, Int $b) {