Dot followed by digits is now treated as a number

nicklockwood · Dec 14, 2017 · 08fef32 · 08fef32
1 parent 06ed90f
commit 08fef32
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Showing 2 changed files with 36 additions and 15 deletions.
diff --git a/Sources/Expression.swift b/Sources/Expression.swift
@@ -1060,24 +1060,40 @@ private extension UnicodeScalarView {
             return nil
         }
 
-        guard var number = scanInteger() else {
-            return nil
-        }
-
-        let endOfInt = self
-        if scanCharacter(".") {
-            if let fraction = scanInteger() {
-                number += "." + fraction + (scanExponent() ?? "")
+        func scanNumber() -> String? {
+            var number: String
+            var endOfInt = self
+            if let integer = scanInteger() {
+                if integer == "0", scanCharacter("x") {
+                    return "0x\(scanHex() ?? "")"
+                }
+                endOfInt = self
+                if scanCharacter(".") {
+                    guard let fraction = scanInteger() else {
+                        self = endOfInt
+                        return integer
+                    }
+                    number = "\(integer).\(fraction)"
+                } else {
+                    number = integer
+                }
+            } else if scanCharacter(".") {
+                guard let fraction = scanInteger() else {
+                    self = endOfInt
+                    return nil
+                }
+                number = ".\(fraction)"
             } else {
-                self = endOfInt
+                return nil
             }
-            number += scanExponent() ?? ""
-        } else if let exponent = scanExponent() {
-            number += exponent
-        } else if number == "0" {
-            if scanCharacter("x") {
-                number = "0x\(scanHex() ?? "")"
+            if let exponent = scanExponent() {
+                number += exponent
             }
+            return number
+        }
+
+        guard let number = scanNumber() else {
+            return nil
         }
         guard let value = Double(number) else {
             return .error(.unexpectedToken(number), number)

diff --git a/Tests/ExpressionTests.swift b/Tests/ExpressionTests.swift
@@ -377,6 +377,11 @@ class ExpressionTests: XCTestCase {
         XCTAssertEqual(try expression.evaluate(), -0.34)
     }
 
+    func testLeadingDecimalPoint() {
+        let expression = Expression(".5")
+        XCTAssertEqual(try expression.evaluate(), 0.5)
+    }
+
     func testExponential() {
         let expression = Expression("1234e5")
         XCTAssertEqual(try expression.evaluate(), 1234e5)