Don't evaluate a lone decimal point to zero

Bug: 22917707

Make a constant consisting of just a decimal point produce an error
when evaluated.

Change-Id: I970c8b396894f301553171dad3c325ffac09ff57
(cherry picked from commit fa5203c051fb5139c8fc678cae3997c8a7293c84)

1 files changed, 11 insertions, 4 deletions

diff --git a/src/com/android/calculator2/CalculatorExpr.java b/src/com/android/calculator2/CalculatorExpr.java
index b387e8b..77e53ea 100644
--- a/src/com/android/calculator2/CalculatorExpr.java
+++ b/src/com/android/calculator2/CalculatorExpr.java
@@ -217,12 +217,19 @@ class CalculatorExpr {
         }
 
         /**
-         * Return BoundedRational representation of constant.
-         * Never null.
+         * Return BoundedRational representation of constant, if well-formed.
+         * Result is never null.
          */
-        public BoundedRational toRational() {
+        public BoundedRational toRational() throws SyntaxException {
             String whole = mWhole;
-            if (whole.isEmpty()) whole = "0";
+            if (whole.isEmpty()) {
+                if (mFraction.isEmpty()) {
+                    // Decimal point without digits.
+                    throw new SyntaxException();
+                } else {
+                    whole = "0";
+                }
+            }
             BigInteger num = new BigInteger(whole + mFraction);
             BigInteger den = BigInteger.TEN.pow(mFraction.length());
             if (mExponent > 0) {