efsInternal and function pointer arg issue (not as the first arg)

[jphelps]

While debugging some code that passes a function pointer to efsInternal (not as its first parameter) I realized there was a problem when creating two series. Specifically, it seems that under certain circumstances the second series to be created always contains the first series' values.

I whittled my original code down to the test code that follows, plus I added a few extra test cases. I would be appreciative if anybody could tell me why the two approaches that don't seem to work display their horizontal lines on top of each other instead of separately? I.e. why do their series have the same values? Thx.

Jeff

function preMain()
{
    var fp = new FunctionParameter("approach", FunctionParameter.STRING);
    fp.addOption("doesntwork");
    fp.addOption("doesntworkeither");
    fp.addOption("butthisworks");
    fp.addOption("andthisworkstoo");
    fp.setDefault("doesntwork");
}

var series1 = null;
var series2 = null;
var fullyInitialized = null;

function main(approach)
{
    if (!fullyInitialized)
    {
    if (approach == "doesntwork")
    {
        if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1]);
        if (series2 == null)
                series2 = efsInternal("functionProxy", regurgitate, [2]);
    }
    else if (approach == "doesntworkeither")
    {
        if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1]);
        if (series2 == null)
                series2 = efsInternal("functionProxy", anotherRegurgitate, [2]);
    }
    else if (approach == "butthisworks")
    {
        if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1]);
        if (series2 == null)
                series2 = efsInternal("anotherFunctionProxy", regurgitate, [2]);
    }
    else if (approach == "andthisworkstoo")
    {
        if (series1 == null)
                series1 = efsInternal("regurgitate", 1);
        if (series2 == null)
                series2 = efsInternal("regurgitate", 2);
    }
    else
    {
        throw "oops!";
    }
        fullyInitialized = true;
    }

    if (getCurrentBarIndex() == -4)
    {
    debugPrintln(approach);
    debugPrintln("  series1 = " + series1.getValue(0));
    debugPrintln("  series2 = " + series2.getValue(0));
    }

    return [series1.getValue(0), series2.getValue(0)];
}

function functionProxy(functionPtr, args)
{
    return functionPtr.apply(null, args);
}

function anotherFunctionProxy(functionPtr, args)
{
    return functionPtr.apply(null, args);
}

function regurgitate(arg)
{
    return arg;
}

function anotherRegurgitate(arg)
{
    return arg;
} 

[jphelps]

It seems the problem has nothing to do with function pointers. I added the "howeverthisdoesntwork" test case (see the new code below) and got the undesired behavior. That case is very similar to the "andthisworkstoo" case, so it appears that passing an array of values as a parameter to efsInternal is what is causing the problem. Is this a misuse of efsInternal on my part?

function preMain()
{
    var fp = new FunctionParameter("approach", FunctionParameter.STRING);
    fp.addOption("doesntwork");
    fp.addOption("doesntworkeither");
    fp.addOption("butthisworks");
    fp.addOption("andthisworkstoo");
    fp.addOption("howeverthisdoesntwork");
    fp.setDefault("doesntwork");
}

var series1 = null;
var series2 = null;
var fullyInitialized = null;

function main(approach)
{
    if (!fullyInitialized)
    {
        if (approach == "doesntwork")
        {
            if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1]);
            if (series2 == null)
                series2 = efsInternal("functionProxy", regurgitate, [2]);
        }
        else if (approach == "doesntworkeither")
        {
            if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1]);
            if (series2 == null)
                series2 = efsInternal("functionProxy", anotherRegurgitate, [2]);
        }
        else if (approach == "butthisworks")
        {
            if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1]);
            if (series2 == null)
                series2 = efsInternal("anotherFunctionProxy", regurgitate, [2]);
        }
        else if (approach == "andthisworkstoo")
        {
            if (series1 == null)
                series1 = efsInternal("regurgitate", 1);
            if (series2 == null)
                series2 = efsInternal("regurgitate", 2);
        }
        else if (approach == "howeverthisdoesntwork")
        {
            if (series1 == null)
                series1 = efsInternal("regurgitate", [1]);
            if (series2 == null)
                series2 = efsInternal("regurgitate", [2]);
        }
        else
        {
            throw "oops!";
        }
        fullyInitialized = true;
    }

    if (getCurrentBarIndex() == -4)
    {
        debugPrintln(approach);
        debugPrintln("  series1 = " + series1.getValue(0));
        debugPrintln("  series2 = " + series2.getValue(0));
    }

    return [series1.getValue(0), series2.getValue(0)];
}

function functionProxy(functionPtr, args)
{
    return functionPtr.apply(null, args);
}

function anotherFunctionProxy(functionPtr, args)
{
    return functionPtr.apply(null, args);
}

function isArray(obj)
{
    return (obj!==null) && (obj!=undefined) && (obj.constructor == Array);
}

function regurgitate(arg)
{
    if (isArray(arg))
        return arg[0];
    else
        return arg;
}

function anotherRegurgitate(arg)
{
    return arg;
} 

[eSignal_JasonK]

Hello jphelps,

Thanks for posting your code examples.

The efsInternal() and efsExternal() have a built-in mechanism to first check to see if a series object with the same parameters has already been created. If one exists the variable is assigned to the existing series object. A second instance of the object is not created. This was done to avoid an "out of memory" problem that would occur prior to EFS2 where a user would do something like below.

function main() {
    var ma = new MAStudy(...);
} 

The EFS1 engine would create a new instance of an MAStudy() object each time main() was executed. This would eventually fill up all available memory.

The EFS2 engine resolves this problem. One of the main reasons for developing the EFS2 functions was to help get away from using JavaScript arrays as this adds complexity for the more novice programmers. We didn't anticipate that arrays would be used as parameters in the manner in which you currently are.

At this point I'm sure you're thinking that an array of [1] is different than [2] so there shouldn't be a problem. These two arrays do contain different values. That part is true. However, the EFS2 engine is not looking at the values within these arrays. It is only looking at what this parameter is. In essence, it sees an Array object of size 1. So, in your following example,

if (approach == "doesntwork")
        {
            if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1]);
            if (series2 == null)
                series2 = efsInternal("functionProxy", regurgitate, [2]);
        } 

series1 instantiates the series object, which the EFS2 engine sees as functionProxy(pointer to regurgitate, Array of size 1).

When efsInternal() is evaluated for the series2 variable, the engine sees functionProxy(pointer to regurgitate, Array of size 1) and thinks this object with these parameters has already been created. So series2 now references the same series object as series1. This is why they both plot a line at 1.

For example sake, if you changed the array size of one of these array parameters as below,

if (approach == "doesntwork")
        {
            if (series1 == null)
                series1 = efsInternal("functionProxy", regurgitate, [1, 1]);
            if (series2 == null)
                series2 = efsInternal("functionProxy", regurgitate, [2]);
        } 

the EFS2 engine now sees series1 with an array parameter of size 2 and series2 with an array parameter of size 1. In this case the parameters are different and will initialize two unique series objects, which will then plot at line at 1 and 2 as expected. Hope this helps.

[jphelps]

Jason,

Thanks for the explanation. FWIW, before reading your reply I had already trudged forward with a solution where I put the array into a unique global variable, passed the name of that variable to the function used by efsInternal, and then accessed the array stored in that global var from within the function when it gets called. This seems to work. However, after reading your response and experimenting a little I have decided to do away with the global var approach and simply add an unused unique string parameter to the function's parameter list. As long as that string is unique it seems to work fine (which is probably the sole reason the global var approach worked.) Thanks for your help.

Jeff

[eSignal_JasonK]

Hello Jeff,

You're most welcome.

I like your solution for adding the additional unused string parameter as well. Great idea.