Merge pull request #43 from Justineo/master

Fix #42

Author: Semigradsky

src/__tests__/index.js

@@ -56,6 +56,13 @@ test(
   '100%'
 )
 
+test(
+  'should reduce simple calc (7)',
+  testFixture,
+  'calc(100px + (100px - 100%))',
+  'calc(200px - 100%)'
+)
+
 test(
   'should reduce additions and subtractions (1)',
   testFixture,

src/lib/reducer.js

@@ -124,11 +124,7 @@ function reduceAddSubExpression(node, precision) {
         right: right.left
       }, precision)
       node.right = right.right
-
-      if (node.operator === '-') {
-        node.operator = right.operator === '+' ? '-' : '+'
-      }
-
+      node.operator = op === '-' ? flip(right.operator) : right.operator
       return reduce(node, precision)
     }
     // value + (something + value) => (value + value) + something