I just happened to run into a problem and I can't find a good solution other than a const_cast. The code below is just an example that illustrates my problem.

Assume the function prototype void OutputObjExistence(const ObjTest& theObj); cannot change, although the code inside can. Also assume that the set must be defined as std::set<ObjTest*> theSet;

The question is how can I do this? The currently shown way leads to a compile error (error C2664: cannot convert parameter 1 from 'const class ObjTest *' to 'class ObjTest *const & ') because it is attempting to use the parameter which is const to find the address in the set of non-const pointers.
#include <iostream>
#include <set>

class ObjTest { };
std::set<ObjTest*> theSet;

void OutputObjExistence(const ObjTest& theObj);
bool FindThisObjTest(const ObjTest& theObj);

int main()
    ObjTest savedObjTest;

    // Insert some new pointers and the saved one above.
    theSet.insert(new ObjTest);
    theSet.insert(new ObjTest);
    theSet.insert(new ObjTest);

    // Call something needing a const reference.

    // Clean up memory.
    std::set<ObjTest*>::iterator iterObj = theSet.begin();
    std::set<ObjTest*>::iterator iterEnd = theSet.end();
    for (; iterObj != iterEnd; ++iterObj)
        if (*iterObj != &savedObjTest)
            delete *iterObj;

    return 0;

// Parameter must be const reference here.
void OutputObjExistence(const ObjTest& theObj)
    // Pass the reference to the Find method.
    if (FindThisObjTest(theObj))
        std::cout << "Found." << std::endl;
        std::cout << "Not found." << std::endl;

// Don't care what the parameter is, but it must work.
bool FindThisObjTest(const ObjTest& theObj)
    return theSet.find(&theObj) != theSet.end();  // Compiler error.