fixed subtraction

DeimosProject · Mar 30, 2016 · 351fb35 · 351fb35
1 parent 50b884c
commit 351fb35
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Showing 2 changed files with 6 additions and 1 deletion.
diff --git a/src/Deimos/Expressions/Subtraction.php b/src/Deimos/Expressions/Subtraction.php
@@ -12,7 +12,10 @@ class Subtraction extends Addition
     public function operate(\SplStack $stack)
     {
         $left = $stack->pop()->operate($stack);
-        $right = $stack->pop()->operate($stack);
+        $right = 0;
+        if ($stack->count()) {
+            $right = $stack->pop()->operate($stack);
+        }
         return $right - $left;
     }
 

diff --git a/tests/Deimos/MathTest.php b/tests/Deimos/MathTest.php
@@ -15,6 +15,7 @@ public function testExampleSub()
     {
         $math = new Math();
         $this->assertEquals($math->evaluate('2 -3 '), -1);
+        $this->assertEquals($math->evaluate('-2 -3 '), -5);
     }
 
     public function testExampleMul()
@@ -45,6 +46,7 @@ public function testExampleNumber()
     {
         $math = new Math();
         $this->assertEquals($math->evaluate('77777'), 77777);
+        $this->assertEquals($math->evaluate('-77777'), -77777);
     }
 
     public function testExampleParenthesis()