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    <p>The syntax for the type you requested would be <code>std::map&lt;std::string, std::multimap&lt;float, pptr&gt;*&gt;</code>, but you don't need to use a pointer; you could just use <code>std::map&lt;std::string, std::multimap&lt;float, pptr&gt; &gt;</code></p> <p><code>std::map::operator[]</code> automatically default-constructs an entry and inserts it when the key requested is not present so if the mapped type is <code>std::multimap&lt;float, pptr&gt;</code>, it will automatically construct the multimap corresponding to a specific key in the map when it is needed. For example:</p> <pre><code> std::map&lt;std::string, std::multimap&lt;float, pptr&gt; &gt; myMap; std::multimap&lt;float, pptr&gt;&amp; myMap_A = myMap["A"]; </code></pre> <p>If the mapped type is <code>std::multimap&lt;float, pptr&gt;*</code> then it's just a raw pointer, so it would be initialized to <code>nullptr</code> (0), and you would need to manually detect that, allocate a new multimap for that key, and store its address. You would also need to make sure that you iterate through the map and <code>delete</code> all the dynamically allocated multimaps before the map is destroyed, and make sure that you never overwrite a non-null pointer without <code>delete</code>ing its multimap first. All of this is can be avoided by not using raw pointers as the mapped type. In fact, you should in general avoid using raw pointers that have ownership of their data; use <a href="https://stackoverflow.com/questions/106508/what-is-a-smart-pointer-and-when-should-i-use-one/106614#106614">smart pointers</a> instead.</p> <p>One last note: Using floating point types as container keys is somewhat risky, since it's quite easy to encounter values that are not quite equal due to rounding errors.</p>
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    1. POC++ map of pointers to maps
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    1. COThanks bcrist. Wondering if it is possible to dynamically generate the variable name myMap_A - from input variable "A" by some means which in turn can be used above ( might not be technically possible - but thought of asking ).
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    2. COI think you might be somewhat confused about variables. The only way to create a variable name is put it into a source or header file. The compiler then decides where that variable's data will be stored. You can't "generate" new variable names at runtime. When you want to refer to data located somewhere else, you need to use references or pointers, as in `std::multimap<float, pptr>& myMap_A = myMap["A"];`
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