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POC++ dynamic (multi-stage) 3D vector instantiation and element assignment
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  1. POC++ dynamic (multi-stage) 3D vector instantiation and element assignment
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    copied!<p>Okay, so I need to create a 3D data-structure at run-time, I decided to use std::vector, the problem is as follows: I know the dimension of the 1st dimension at instantiation time (when I create the object I'm using it in), but I don't know the dimension of the second until run-time, and the size of 3rd dimensions can vary. <strong>I have created the 3D vector</strong> and the run-time doesn't complain, however I'm having difficulty <strong>assigning values</strong> to the elements.</p> <p>This code is part of an object I'm creating. In the class definition I have:</p> <pre><code>std::vector&lt; std::vector&lt; std::vector&lt;double&gt; &gt; &gt; splits; </code></pre> <p>Then in the object constructor, in order to create/allocate the first dimension, I have:</p> <pre><code>for(int i=0; i&lt;sizeOfDimOne; i++){ //create 1st dimension splits.push_back( std::vector&lt; std::vector&lt;double&gt; &gt;() ); } </code></pre> <p>based on user input I need to create 2nd dimension of a certain size, I call a method for this:</p> <pre><code>for(int i=0; i&lt;sizeOfDimOne; i++){ for(int j=0; j&lt;sizeOfDimTwo; j++) //create second dimension splits[i].push_back( std::vector&lt;double&gt;() ); } </code></pre> <p>However, when I get to assigning values:</p> <pre><code>for(int i=0; i&lt;sizeOfDimThree; i++){ splits[dim1][dim2].push_back( someValue ); //adding an element to the 3rd dim } </code></pre> <p>(The <em>someValue</em> changes constantly (and is a double), and you don't have to worry about lower dimension indexing, everything checks out.) The problem is - when I checked <em>splits[dim1][dim2][i]</em> the value was <strong><em>0.0</em></strong> for (presumably all) entries, naturally this is not what was provided by <em>someValue</em>.</p> <p>I have also tried creating the 3rd dimension using <em>.resize(sizeOfDimThree)</em> and then assigning using</p> <pre><code>splits[dim1][dim2][i] = whatever; </code></pre> <p>but that didn't work at all - no object/element was created at all.</p> <p>I realize this perhaps isn't the most straight forward manner of phrasing the question, but I believe it is the most accurate, as there might be multiple-points of failure.</p>
 

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