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POLine management in a text editor
 

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    <p>I've been working on a text editor for some time. I made a custom edit control, from scratch, and I've got the basics down now. The problem I am facing is regarding line management. Since, my program relies on dividing the input text into lines(the text is printed line by line), line management is pretty important. I was using std::vector to store the line positions. I am using a Piece Table for my text processing, but for the sake of simplicity, let's say that I have an array of characters. I add/insert an element into the line vector every time the user presses enter. The issue is that every time the user inserts a character, the whole structure is disturbed. For example : </p> <pre><code> 0 1 2 3 4 5 6 7 8 9 10 text = ['h','e','l','l','o','\n','W','o','r','l','d'] state of line vector : line[0] = 0 line[1] = 6 </code></pre> <p>Let's say the user inserts a character('x') after the text[2]:</p> <pre><code> 0 1 2 3 4 5 6 7 8 9 10 11 text = ['h','e','l','x','l','o','\n','W','o','r','l','d'] state of line vector : line[0] = 0 line[1] = 6 </code></pre> <p>Because of the insertion, I would need to update the value of each element in the lines vector after the current line. The same for deletion. If there are 1000 lines in a program and the user edits the first line, it would be quite inefficient to update all 999 elements(except the first one). </p> <p>What I was thinking of was to keep each line independent of each other. But that would lead to complications when an existing line is divided into two lines. So I'd like to know what's a good way to go about the problem?</p> <p>Edit: Just to clarify, I am using a data structure called Piece Table. I am not using an array of characters. Here is what a piece table data structure is : <a href="http://www.cs.unm.edu/~crowley/papers/sds.pdf" rel="nofollow">http://www.cs.unm.edu/~crowley/papers/sds.pdf</a></p>
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    1. USAdrian McCarthy
    1. USdevjeetroy
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    1. COClearly vector<> is the wrong choice of data structure if you want to support cheap inserts. O(n) complexity. Have you considered list<>?
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      1. USHans Passant
    2. CO@HansPassant if you mean storing a line per element in the list, that would be expensive for moving from one line to another (though admittedly inserting a line is probably more common than moving from one line to another)
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    3. COYou haven't really described the problem that you're trying to solve. For instance, do you need O(1) access to the Nth line, or will O(N) do? (If so, you could simply keep the lengths of the lines in your vector, and add them up where necessary.)
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      1. USNeil
 

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