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POPassing a MathLink Function Lists With Different Structures
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copied!<p>I've been developing a MathLink application with a function that accepts two lists, e.g.</p> <pre><code>:Pattern: g[zi_List, fi_List] </code></pre> <p>which I intended to pull in to the function manually. Both lists can be real or complex with the result being complex if either parameter is complex. Additionally, <code>fi</code> could be a list of square matrices, but <code>zi</code> is to remain a one dimensional list. </p> <p>Within the <a href="http://reference.wolfram.com/mathematica/guide/AlphabeticalListingOfMathLinkCFunctions.html" rel="nofollow">MathLink C API</a>, the most straightforward seeming function to use is <a href="http://reference.wolfram.com/mathematica/ref/c/MLGetReal64Array.html" rel="nofollow"><code>MLGetReal64Array</code></a> which can handle both real and complex data types as <code>Complex</code> shows up as the innermost <code>Head</code> of the array. And, once complexity is determined, the array can be cast to <code>std::complex<double></code> or the C99 complex type, if appropriate. Now, <code>MLGetReal64Array</code> doesn't handle non-rectangular <code>Lists</code>, so each <code>List</code> element must have the dimensionality of the others and be of the same type: real of complex. Oddly, though, with a function that accepts a single <code>List</code> parameter, <code>MLGetReal64Array</code> returns a data structure that has a one element <code>List</code> as its outermost element, i.e. inputing <code>h[ {1, 3, 5} ]</code> returns <code>List[List[1,3,5]]</code> on the c-side of things. </p> <p>It turns out that for a two list function, like <code>g</code>, a single call to <code>MLGetReal64Array</code> will return both parameters at once, i.e. <code>g</code> receives <code>List[ zi, fi ]</code>. Since I plan on preprocessing each list for uniformity of structure and element type, ensuring that both had the same element type wouldn't be a problem. But, I'd like for <code>fi</code> to be a list of matrices, and <code>MLGetReal64Array</code> causes a <code>MLEGSQ: MLGet() called out of sequence</code> error.</p> <p>So, my questions are: can I use <code>MLGetReal64Array</code> to get both lists? how would I go about it? And, if I can't use <code>MLGetReal64Array</code>, what are my alternatives?</p> <p>I'm thinking that if <code>MLGetReal64Array</code> is correct about the structure, I can pop the outer <code>List</code> off the link by using <a href="http://reference.wolfram.com/mathematica/ref/c/MLGetFunction.html" rel="nofollow"><code>MLGetFunction</code></a> which would then allow me to use <code>MLGetReal64Array</code> for each parameter. As of yet, I haven't tried it. But, in the meantime, I would appreciate any suggestions.</p>

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