Add first demo of new syntax editor

As part of the GF cloud stuff, it can be accessed from
http://cloud.grammaticalframework.org/syntax-editor/editor.html

src/www/syntax-editor/js/ast.js

@@ -0,0 +1,131 @@
+/* --- Tree representation -------------------------------------------------- */
+function Tree(value) {
+
+    // Create node as JS object
+    var createNode = function(value, children) {
+        var node = {
+            value: value,
+            children: []
+        };
+        if (children != undefined)
+            for (c in children)
+                node.children.push( createNode(children[c],[]) );
+        return node;
+    }
+
+    this.root = createNode(value, []);
+
+    // add value as child of id
+    this.add = function(id, value, children) {
+        var x = this.find(id);
+        x.children.push( createNode(value, children) );
+    }
+
+    // id should be a list of child indices [0,1,0]
+    // or a string separated by commas "0,1,0"
+    this.find = function(_id) {
+        var id = undefined
+        switch (typeof _id) {
+        case "number": id = [_id]; break;
+        case "string": id = _id.split(","); break;
+        case "object": id = _id.get().slice(); break; // clone NodeID array
+        }
+        var node = this.root;
+        if (id[0] == 0) id.shift();
+        while (id.length>0 && node.children.length>0) {
+            node = node.children[id.shift()];
+        }
+        if (id.length>0)
+            return undefined;
+        return node;
+    }
+}
+
+/* --- ID for a node in a tree ---------------------------------------------- */
+function NodeID(x) {
+    this.id = new Array();
+    this.id.push(0);
+
+    // Initialize from input
+    if (x) {
+        switch (typeof x) {
+        case "number": this.id = [x]; break;
+        case "string": this.id = map(function(s){return parseInt(s)}, x.split(",")); break;
+        case "object": this.id = x.get().slice(); break; // another NodeID
+        }
+    }
+
+    // get id
+    this.get = function() {
+        return this.id;
+    }
+    
+    // Add child node to id
+    this.add = function(x) {
+        this.id.push(parseInt(x));
+        return this.id;
+    }
+
+    // compare with other id
+    this.equals = function(other) {
+        return JSON.stringify(this.id)==JSON.stringify(other.id);
+    }
+
+}
+
+/* --- Abstract Syntax Tree (with state)------------------------------------- */
+function AST(fun, cat) {
+
+    function Node(fun, cat) {
+        this.fun = fun;
+        this.cat = cat;
+    }
+
+    this.tree = new Tree(new Node(fun, cat));
+    this.current = new NodeID(); // current id in tree
+
+    this.getFun = function() {
+        return this.tree.find(this.current).value.fun;
+    }
+    this.setFun = function(f) {
+        this.tree.find(this.current).value.fun = f;
+    }
+    this.getCat = function() {
+        return this.tree.find(this.current).value.cat;
+    }
+    this.setCat = function(c) {
+        this.tree.find(this.current).value.cat = c;
+    }
+
+    this.add = function(fun, cat) {
+        this.tree.add(this.current, new Node(fun,cat));
+    }
+    
+    // Clear children of current node
+    this.removeChildren = function() {
+        this.tree.find(this.current).children = [];
+    }
+
+    // Move current id to child number i
+    this.toChild = function(i) {
+        this.current.add(i);
+    }
+
+    // Return tree as string
+    this.toString = function() {
+        var s = "";
+        function visit(node) {
+            s += node.value.fun ? node.value.fun : "?" ;
+            if (node.children.length == 0)
+                return;
+            for (i in node.children) {
+            s += "(";
+                visit(node.children[i]);
+            s += ")";
+            }
+        }
+        visit(this.tree.root);
+        return s;
+    }
+}
+