Re: ? Define Constant Name Strings to Integer Values

"Doug Harrison [MVP]" <>
Wed, 09 Jul 2008 23:39:29 -0500
On Wed, 9 Jul 2008 20:21:31 -0400, "Alec S." <@> wrote:


I'm looking for a way to convert a defined constant from its name to its value.
For example I need a way to take the input string "VK_ESCAPE" and derive its
integer value 0x1b.

Most scripting languages do this through the eval function, but I cannot figure
out a way to accomplish this with VC++.

(I'm writing a dialog app, and I need a way to allow the user to pass key names
on the command line without reinventing an entire key-map.)

Any ideas? Thanks.

You will have to perform the mapping yourself, e.g.

#include <afx.h>

#include <iostream>
#include <map>

// I assume you want case-insensitive ordering.
struct LessNoCase
   bool operator()(const CString& x, const CString& y) const
      return x.CompareNoCase(y) < 0;

typedef std::map<CString, int, LessNoCase> CStringIntMap;
CStringIntMap::value_type const keyNameData[] =
   CStringIntMap::value_type(_T("VK_ESCAPE"), 0x1b),
   // add more...
CStringIntMap const keyNameMap(

int main()
   CStringIntMap::const_iterator i = keyNameMap.find(_T("vk_escape"));
   if (i != keyNameMap.end())
      std::cout << i->first << " = " << i->second << '\n';

Of course, if there are just a few pairs in the map, you could get rid of
the map and linearly search the unsorted array keyNameData, and it would
probably be faster. The generated code would certainly be smaller.

Doug Harrison
Visual C++ MVP

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