Code Generator

        /* terminals used */
        var num, id_var, id_func, id_idx, binaryOP, quote, assignOP;

        /* non-terminals used */
        var Program, Assertion, Expr, TableExpr, Constant, FunctionDef, ColumnDef, Stmt, Assign, Condition, Call, Loop;


        // non terminal class
        function NonTerminal(name) {
            this.name = name;
            this.rules = [];
            this.addRule = function (rule) {
                this.rules.push(rule);
            };
            this.getRandomRule = function () {
                if (this.rules.length == 0) {
                    return "";
                }
                return getRandomArrayElement(this.rules);
            };
            this.derive = function () {
                console.log("derive: " + this.name);
                return (this.getRandomRule())();
            };
        }

        // terminal class
        function Terminal(name, deriveFunc) {
            this.name = name;
            this.derive = deriveFunc;
        };

    /* --------- TERMINALS --------- */
        /* Number */
        num = new Terminal("Num", function () {
            return Math.round(Math.random() * 10);
        });

        /* ID */
        id_var = new Terminal("ID", function () {
            return getRandomArrayElement(varIds);
        });

        id_func = new Terminal("ID", function () {
            return getRandomArrayElement(funcIds);
        });

        id_idx = new Terminal("ID", function () {
            return getRandomArrayElement(idxIds);
        });

        /* OP */
        binaryOP = new Terminal("OP", function () {
            if($scope.nonAssoc){
                return getRandomArrayElement(binaryOpsWithNonAssoc);
            }
            else{
                return getRandomArrayElement(binaryOps);
            }
        });

        /* QUOTE */
        quote = new Terminal("QUOTE", function () {
            return getRandomArrayElement(quotes);
        });

        /* ASSIGN OP */
        assignOP = new Terminal("assignOP", function () {
            return getRandomArrayElement(assignOps);
        });

        /* --------- NON-TERMINALS --------- */

        /* Program */
        Program = new NonTerminal("Program");
        Program.addRule(function () {
            return Assertion.derive();
        });
        Program.addRule(function () {
            return Constant.derive();
        });
        Program.addRule(function () {
            return FunctionDef.derive();
        });
        Program.addRule(function () {
            return ColumnDef.derive();
        });

        /* Assertion */
        Assertion = new NonTerminal("Assertion");
        Assertion.addRule(function () {
            return "assert " + Expr.derive() + " : " + quote.derive();
        });


        /* TableExpr */
        TableExpr = new NonTerminal("TableExpr");
        TableExpr.addRule(function () {
            return "COLS";
        });
        TableExpr.addRule(function () {
            return "ROWS";
        });
        TableExpr.addRule(function () {
            return "TABLE[" + Expr.derive() + "][" + Expr.derive() + "]";
        });

        /* Expr */
        Expr = new NonTerminal("Expr");
        Expr.addRule(function () {
            return num.derive();
        });
        Expr.addRule(function () {
            return id_var.derive();
        });
        Expr.addRule(function () {
            return Expr.derive() + " " + binaryOP.derive() + " " + Expr.derive();
        });
        Expr.addRule(function () {
            return "-" + Expr.derive();
        });
        Expr.addRule(function () {
            return "( " + Expr.derive() + " )";
        });
        Expr.addRule(function () {
            return TableExpr.derive();
        });
        Expr.addRule(function () {
            return Call.derive();
        });

        /* Stmt */
        Stmt = new NonTerminal("Stmt");
        Stmt.addRule(function () {
            return Expr.derive()
        });
        Stmt.addRule(function () {
            return Assign.derive()
        });
        Stmt.addRule(function () {
            return Condition.derive()
        });
        //Stmt.addRule(function () { return Loop.derive() });

        /* Constant */
        Constant = new NonTerminal("Constant");
        Constant.addRule(function () {
            return "var " + id_var.derive() + " = " + Expr.derive();
        });

        /* FunctionDef */
        FunctionDef = new NonTerminal("FunctionDef");
        FunctionDef.addRule(function () {
            return "def " + id_func.derive() + "(" + makeList(id_var, ",", false) + "){\n" + makeList(Stmt, ";", true) + "\n}"
        });

        /* ColumnDef */
        ColumnDef = new NonTerminal("ColumnDef");
        ColumnDef.addRule(function () {
            return "def TABLE[" + Expr.derive() + "][" + id_idx.derive() + "] {\n" + makeList(Stmt, ";", true) + "\n}"
        });

        /* Assign */
        Assign = new NonTerminal("Assign");
        Assign.addRule(function () {
            return id_var.derive() + " " + assignOP.derive() + " " + Expr.derive();
        });

        /* Condition */
        Condition = new NonTerminal("Condition");
        Condition.addRule(function () {
            return "if(" + Expr.derive() + "){\n" + makeList(Stmt, ";", true) + "\n}";
        });
        Condition.addRule(function () {
            return "if(" + Expr.derive() + "){\n" + makeList(Stmt, ";", true) + "\n} else {\n" + makeList(Stmt, ";", true) + "\n}";
        });

        /* Call */
        Call = new NonTerminal("Call");
        Call.addRule(function () {
            return id_func.derive() + "(" + makeList(Expr, ",", false) + ")";
        });

        /* Loop */
        Loop = new NonTerminal("Loop");
        Loop.addRule(function () {
            return "for ( " + id_idx.derive() + " = " + Expr.derive() + ".." + Expr.derive() + " ) {\n" + makeList(Stmt, ";", true) + "\n}";
        });

        /* Utils */

        // get a random element from an array
        function getRandomArrayElement(arr) {
            return arr[Math.floor(Math.random() * arr.length)];
        }

        // create a list of 0+ elements
        function makeList(item, seperator, isBody) {
            var listSize = Math.round(Math.random() * MAX_LIST_SIZE);
            var res = "";

            for (var i = 0; i < listSize; i++) {
                if (isBody) {
                    res += "\t";
                }
                res += item.derive();
                if (i != listSize - 1) {
                    res += seperator;
                    if (isBody) {
                        res += "\n";
                    }
                }
            }

            return res;
        }