Need help in converting C++ to javascript

Question

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Hello all,

I'm constructing a javascript indicator for my client and they gave me below C++ code from their old system. I have never done C++ program before. Below is the part of the C++ code. What I want to know is in the line

if (it3 != d1Swing.end() && it3->x == h[i].x) --(it1 = it2 = it3);

what is the meaning of --(it1 = it2 = it3)? What will it looks like in javascript?

vector<PTPoint::PTIndexPoint> dnSwing;
list<PTPoint::PTIndexPoint> hq, lq;
vector<PTPoint::PTIndexPoint>::iterator it1 = d1Swing.begin(), it2 = d1Swing.begin(), it3 = ++d1Swing.begin();
//
// more code here
//
for (int i = 0; i < period; ++i)
{
    while (!hq.empty() && hq.back().y < h[i].y) hq.pop_back();
    hq.push_back(h[i]);
    while (!lq.empty() && lq.back().y > l[i].y) lq.pop_back();
    lq.push_back(l[i]);
    if (it3 != d1Swing.end() && it3->x == h[i].x) --(it1 = it2 = it3);
    //
    // more code here
    //
}
//
// more code here
//
p->swap(dnSwing);

Thanks in advanced.
tslin

What I have tried:

I've googled for a long time but search include special characters and those characters were used in most of the languages.

Posted 9-Jan-17 17:28pm

tslin89

Updated 9-Jan-17 21:44pm

v2

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Comments

KarstenK 10-Jan-17 3:45am

Tip: use braces and new lines after the while and the if command to make the code clearer.

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CPallini · Accepted Answer · 2017-01-09T21:44:00

Solution 1

Quote:
what is the meaning of --(it1 = it2 = it3)? What will it looks like in javascript?

assign it3 to it2.
assign it2 to it1.
decrement it1.

You may rewrite it (C++ code) this way:

C++

{
  it2 = it3;
  it1 = it2;
  it1 = it1 - 1;
}

I suppose Javascript code would be very similar.

Posted 9-Jan-17 21:44pm

CPallini

Comments

tslin89 10-Jan-17 4:44am

Thanks a lot for the answer.

CPallini 10-Jan-17 6:09am

You are welcome.