optimized implementations of sum() and product()

this is based on code + ideas by @jvasileff in #728, but using native
ceylon · Oct 1, 2015 · c0d88c8 · c0d88c8
1 parent ae32cbc
commit c0d88c8
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diff --git a/src/ceylon/language/product.ceylon b/src/ceylon/language/product.ceylon
@@ -2,7 +2,7 @@
  product of the values.
  
      {Float+} values = ... ;
-     Float result = sum(values);
+     Float result = product(values);
  
  For the case of a possibly-empty stream, form a nonempty 
  stream starting with the unit element (the [[multiplicative
@@ -12,11 +12,52 @@
      Float result = product { 1.0, *values };"
 see (`function sum`)
 tagged("Streams", "Numbers")
-shared Value product<Value>({Value+} values) 
+shared native Value product<Value>({Value+} values) 
+        given Value satisfies Numeric<Value>;
+
+shared native("js") Value product<Value>({Value+} values) 
         given Value satisfies Numeric<Value> {
-    variable value product = values.first;
-    for (val in values.rest) {
+    value it = values.iterator();
+    assert (!is Finished first = it.next());
+    variable value product = first;
+    while (!is Finished val = it.next()) {
         product *= val;
     }
     return product;
 }
+
+shared native("jvm") Value product<Value>({Value+} values) 
+        given Value satisfies Numeric<Value> {
+    value it = values.iterator();
+    switch (first = it.next())
+    case (is Integer) {
+        // unbox; don't infer type Value&Integer
+        variable Integer product = first;
+        while (is Integer val = it.next()) {
+            Integer unboxed = val;
+            product *= unboxed;
+        }
+        assert (is Value result = product);
+        return result;
+    }
+    case (is Float) {
+        // unbox; don't infer type Value&Float
+        variable Float product = first;
+        while (is Float val = it.next()) {
+            Float unboxed = val;
+            product *= unboxed;
+        }
+        assert (is Value result = product);
+        return result;
+    }
+    case (is Finished) {
+        assert (false);
+    }
+    else {
+        variable value product = first;
+        while (!is Finished val = it.next()) {
+            product *= val;
+        }
+        return product;
+    }
+}
diff --git a/src/ceylon/language/sum.ceylon b/src/ceylon/language/sum.ceylon
@@ -12,7 +12,10 @@
      Float total = sum { 0.0, *values };"
 see (`function product`)
 tagged("Streams", "Numbers")
-shared Value sum<Value>({Value+} values) 
+shared native Value sum<Value>({Value+} values) 
+        given Value satisfies Summable<Value>;
+
+shared native("js") Value sum<Value>({Value+} values) 
         given Value satisfies Summable<Value> {
     value it = values.iterator();
     assert (!is Finished first = it.next());
@@ -22,3 +25,39 @@ shared Value sum<Value>({Value+} values)
     }
     return sum;
 }
+
+shared native("jvm") Value sum<Value>({Value+} values) 
+        given Value satisfies Summable<Value> {
+    value it = values.iterator();
+    switch (first = it.next())
+    case (is Integer) {
+        // unbox; don't infer type Value&Integer
+        variable Integer sum = first;
+        while (is Integer val = it.next()) {
+            Integer unboxed = val;
+            sum += unboxed;
+        }
+        assert (is Value result = sum);
+        return result;
+    }
+    case (is Float) {
+        // unbox; don't infer type Value&Float
+        variable Float sum = first;
+        while (is Float val = it.next()) {
+            Float unboxed = val;
+            sum += unboxed;
+        }
+        assert (is Value result = sum);
+        return result;
+    }
+    case (is Finished) {
+        assert (false);
+    }
+    else {
+        variable value sum = first;
+        while (!is Finished val = it.next()) {
+            sum += val;
+        }
+        return sum;
+    }
+}