Support operations between strings and fields, support concatenating

strings.

lib/carto/parser.js

@@ -763,6 +763,7 @@ carto.Parser = function Parser(env) {
                     return new tree.Value(expressions);
                 }
             },
+            // A sub-expression, contained by parenthensis
             sub: function() {
                 var e;
 
@@ -770,12 +771,15 @@ carto.Parser = function Parser(env) {
                     return e;
                 }
             },
+            // This is a misnomer because it actually handles multiplication
+            // and division.
             multiplication: function() {
                 var m, a, op, operation;
                 if (m = $(this.operand)) {
                     while ((op = ($('/') || $('*'))) && (a = $(this.operand))) {
                         operation = new tree.Operation(op, [operation || m, a], memo);
                     }
+                    console.log(m);
                     return operation || m;
                 }
             },
@@ -793,9 +797,7 @@ carto.Parser = function Parser(env) {
             // An operand is anything that can be part of an operation,
             // such as a Color, or a Variable
             operand: function() {
-                return $(this.sub) || $(this.entities.dimension) ||
-                       $(this.entities.color) || $(this.entities.variable) ||
-                       $(this.entities.call);
+                return $(this.sub) || $(this.entity);
             },
 
             // Expressions either represent mathematical operations,

lib/carto/tree/field.js

@@ -4,8 +4,9 @@ tree.Field = function Field(content) {
     this.value = content || '';
     this.is = 'field';
 };
+
 tree.Field.prototype = {
-    toString: function(quotes) {
+    toString: function() {
         return '[' + this.value + ']';
     },
     'eval': function() {

lib/carto/tree/operation.js

@@ -31,16 +31,18 @@ tree.Operation.prototype.eval = function(env) {
     }
 
     if (a instanceof tree.Quoted || b instanceof tree.Quoted) {
-        env.error({
-           message: 'One cannot add, subtract, divide, or multiply strings.',
-           index: this.index,
-           type: 'runtime',
-           filename: this.filename
-        });
-        return {
-            is: 'undefined',
-            value: 'undefined'
-        };
+        if (this.op === '*' || this.op === '/') {
+            env.error({
+               message: 'One cannot add, subtract, divide, or multiply strings.',
+               index: this.index,
+               type: 'runtime',
+               filename: this.filename
+            });
+            return {
+                is: 'undefined',
+                value: 'undefined'
+            };
+        }
     }
 
     return a.operate(this.op, b);

lib/carto/tree/quoted.js

@@ -10,8 +10,14 @@ tree.Quoted.prototype = {
         var xmlvalue = this.value.replace(/\'/g, ''');
         return (quotes === true) ? "'" + xmlvalue + "'" : this.value;
     },
+
     'eval': function() {
         return this;
+    },
+
+    operate: function(op, other) {
+        return new tree.Quoted(this.quote,
+            tree.operate(op, this.toString(), other.toString()));
     }
 };
 

lib/carto/tree/reference.js

@@ -166,6 +166,8 @@ tree.Reference.validValue = function(env, selector, value) {
             }
             return true;
         }
+    } else if (tree.Reference.selector(selector).type == 'expression') {
+        return true;
     } else {
         if (tree.Reference.selector(selector).validate) {
             var valid = false;

test/rendering/field.mss

@@ -1,5 +1,5 @@
 #world {
-  text-name: [NAME];
+  text-name: "hello " + [NAME];
   text-size: 11;
   text-face-name: "Georgia Regular", "Arial Italic";
 }