modulus operator, resolves #1

README.md

@@ -36,6 +36,19 @@ expect(expanded[3][0]).to.equal('2.4.01');
 - ```*```
 - ```even```
 - ```odd```
+- ```% (modulus)```
+
+### Examples
+
+#### Modulus
+
+```js
+> "1.%3.%30"
+= "1.1.01", "1.1.31", "1.1.61", "1.1.91", "1.4.01", "1.4.31", "1.4.61", "1.4.91"
+
+> "1.1.5%20"
+= "1.1.05", "1.1.25", "1.1.45", "1.1.65", "1.1.85"
+```
 
 ## Custom matchers
 
@@ -44,9 +57,8 @@ It is possible to add a custom *matcher callback*, a function which gets execute
 The stack of matchers will continue to execute until a position has been accepted or until the stack ends.
 
 ```js
-expr.addMatcher(function (position, fragments) {
-  if (position === '1.1.45') return true;
-  if (fragments[0] === 1 && fragments[2] === 96) return true;
+expr.addMatcher(function (exprFragments, posFragments) {
+  if (posFragments[2] === 45) return true;
   return false;
 });
 ```
@@ -66,6 +78,7 @@ expr.addMatcher(function (position, fragments) {
 - **1.1.0**
   - CHANGED: expects options object instead of barsPerLoop and beatsPerBar separately [#4](https://github.com/adamrenklint/dilla-expressions/issues/4)
   - NEW: possible to add custom matcher callback [#3](https://github.com/adamrenklint/dilla-expressions/issues/3)
+  - NEW: modulus operator [#1](https://github.com/adamrenklint/dilla-expressions/issues/1)
 
 ## License
 

index.js

@@ -21,7 +21,7 @@ function getPossiblePositions (barsPerLoop, beatsPerBar) {
 function getFragments (position) {
   return position.split('.').map(function (fragment) {
     var fragmentNumber = parseInt(fragment, 10);
-    if (!isNaN(fragmentNumber)) return fragmentNumber;
+    if (fragment.match(/^\d+$/) && !isNaN(fragmentNumber)) return fragmentNumber;
     return fragment;
   });
 }
@@ -35,6 +35,7 @@ function addMatcher (matcher) {
 
 function makeExpressionFunction (expression) {
   var exprFragments = getFragments(expression);
+  // console.log(exprFragments, expression)
   return function expressionFn (position) {
     var positionFragments = getFragments(position);
     var valid = true;
@@ -44,9 +45,16 @@ function makeExpressionFunction (expression) {
       if (exprFragment === 'odd' && positionFragments[index] % 2 === 1) return;
       if (exprFragment === '*') return;
 
-      // if (typeof exprFragment === 'string' && exprFragment.indexOf('%') >= 0) {
-        // console.log('deal with modulus', exprFragment, positionFragments[index])
-      // }
+      // console.log('foo', exprFragment, typeof exprFragment);
+      if (typeof exprFragment === 'string' && exprFragment.indexOf('%') >= 0) {
+        // console.log(exprFragment)
+
+        var nums = exprFragment.split('%');
+        var offset = parseInt(nums[0] || 1, 10);
+        var mod = parseInt(nums[1], 10);
+        var res = (positionFragments[index] - offset) % mod;
+        if (!res) return;
+      }
       // position is invalid, break out early
       // console.log('>', position, positionFragments);
       valid = false;
@@ -57,7 +65,7 @@ function makeExpressionFunction (expression) {
     var matcher;
     while (!valid && _matchers.length) {
       matcher = _matchers.shift();
-      if (matcher(position, positionFragments)) {
+      if (matcher(exprFragments, positionFragments)) {
         valid = true;
       }
     }