From 5b2dc71a35a67a0f52316629e36424c895d9f777 Mon Sep 17 00:00:00 2001
From: John Vasileff <john@vasileff.com>
Date: Thu, 13 Aug 2015 15:28:44 -0400
Subject: [PATCH] optimize sum() for Integers and Floats

This implementation avoids using a boxed type for the `sum`
accumulator variable when summing Integers and Floats.
---
 src/ceylon/language/sum.ceylon | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/src/ceylon/language/sum.ceylon b/src/ceylon/language/sum.ceylon
index 7abcbc3cf..ebe47e89d 100644
--- a/src/ceylon/language/sum.ceylon
+++ b/src/ceylon/language/sum.ceylon
@@ -4,10 +4,33 @@ see (`function product`)
 shared Value sum<Value>({Value+} values) 
         given Value satisfies Summable<Value> {
     value it = values.iterator();
-    assert (!is Finished first = it.next());
-    variable value sum = first;
-    while (!is Finished val = it.next()) {
-        sum += val;
+    value first = it.next();
+    if (is Integer first) {
+        // 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;
+    }
+    else if (is Float first) {
+        // 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;
+    }
+    else {
+        assert (!is Finished first);
+        variable value sum = first;
+        while (!is Finished val = it.next()) {
+            sum += val;
+        }
+        return sum;
     }
-    return sum;
 }