canonicalized arithmetic syntax

lib/arithmetic.js

@@ -30,10 +30,15 @@ function parseExpression(expressionString) {
     if (singleModule)
       moduleName = moduleName.substr(1, moduleName.length - 2);
 
+    var canonicalized = moduleName.substr(0, 1) == '`' && moduleName.substr(moduleName.length - 1, 1) == '`';
+    if (canonicalized)
+      moduleName = moduleName.substr(1, moduleName.length - 2);
+
     operations.push({
       operator: operator,
       moduleName: moduleName,
-      singleModule: singleModule
+      singleModule: singleModule,
+      canonicalized: canonicalized
     });
   }
 
@@ -82,18 +87,23 @@ function expandGlobAndCanonicalize(builder, operation) {
   var loader = builder.loader;
 
   // no glob -> just canonicalize
-  if (operation.moduleName.indexOf('*') == -1)
+  if (operation.moduleName.indexOf('*') == -1) {
+    if (operation.canonicalized)
+      return [operation];
+
     return loader.normalize(operation.moduleName)
     .then(function(normalized) {
       operation.moduleName = builder.getCanonicalName(normalized);
       return [operation];
     });
+  }
 
   // globbing
   var metadata = {};
   var globSuffix = operation.moduleName[operation.moduleName.length - 1] == '*';
   var pluginSyntax = operation.moduleName.indexOf('!') != -1;
-  return loader.normalize(operation.moduleName)
+
+  return Promise.resolve(operation.canonicalized ? loader.decanonicalize(operation.moduleName) : loader.normalize(operation.moduleName))
   .then(function(normalized) {
     // remove ALL extension adding when globbing
     if (globSuffix) {