问Mathjs自定义和函数

EN

// works 
  sumFromTo(i,1,10,i+1)  // = 65

// works not because x is undefined
test(x) = sumFromTo(i,1,x,i+1) 
test(10)

function sumFromTo(iteratorName, from, to, toString, f) {
    var total = 0;
    var toVal = typeof to == "number" ? to : to.length;
    for (var iterator = from; iterator <= toVal; iterator++) {
        mathScope[iteratorName] = iterator;
        mathScope[toString + "_" + iterator] = to[iterator];
        total += math.eval(f, mathScope);
    }
    return total;
}
sumFromTo.transform = function (args, math, scope) {
    /*   Iterator    */
    var iteratorName = "notfound";
    if (args[0] instanceof math.expression.node.SymbolNode) {
        iteratorName = args[0].name;
    } else {
        throw new Error('First argument must be a symbol');
    }

    /*    Startvalue of Iterator    */
    if (args[1] instanceof math.expression.node.ConstantNode) {
        if (args[1].value == 0) {
            throw new Error('Sum must counting from >=1: 0 given');
        }
    }

    /*    to: Array to loop    */
    if (args[2] instanceof math.expression.node.SymbolNode) {
        var toString = args[2].name;
    }

    /*    compile    */
    var from = args[1].compile().eval(scope);
    scope[iteratorName] = from;
    var to = args[2].compile().eval(scope);

    if (to.constructor.name == "Matrix") {
        to = to.toArray();
        scope[toString] = to;
    }else{
        if(typeof to == "object"){
            to = to.toArray();
        }
    }
    return sumFromTo(iteratorName, from, to, toString, args[3].toString());
};
sumFromTo.transform.rawArgs = true;
math.import({sumFromTo: sumFromTo}, {override: true});