Utility - Helper Functions

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Introduction

In my earlier article "The Standalone Programmer", I mentioned that I have a bad habit of accidentally using the set operator (=) in if statements where I intend to use the equality operator (==).  To put an end to this habit, I have written some simple helper functions to eliminate this problem altogether.  I decided to write this simple article and post the code for these functions (and a few others) in the hopes that someone else will find them useful.

My primary objective in writing these functions was to eliminate some of my most common programming mistakes and to simplify some of the more common tasks I find myself performing.  I have provided the code in the form of 2 files: HelperFunctions1.h and HelperFunctions1.cpp.  

The Equality Operator

As I said, I have a bad habit of using the set operator incorrectly in conditional statements.  I can't remember how many times I have written code like the code below and it has bitten me badly on occasion.

if (iValue1 = iValue2)
{
    ...bla.bla.bla
}

One good habit to get into is to always put constant values on the left side of such conditionals because the compiler will detect the problem before the code ever gets executed.  This is a good habit, but is limited to situations where a constant is involved.  Many (if not most) of the situations I encounter involve 2 non-const variables.  To combat this issue, I have written several simple helper functions to use in place of the equality operator. Below is a list of these functions.  Each is inline so that they do not adversely impact performance.  Each of these functions take 2 const parameters of a specific data type and perform an equality comparison on them.  The string related functions use the strcmp and stricmp operators.  (I chose to write the string comparison functions because I also misuse these operators by expecting a bool return value instead of an int.)  The function names and prototypes should be self explanatory.

With these operators I can now write code like the code below eliminating the problems with the equality operator.

   if (IsEqual(iValue1, iValue2))
   {
      ...bla.bla.bla
   }

Type Conversions

Less of a problem but still irritating to me is situations where I need to convert a string to a numeric value or visa-versa.  I like many of you must program in C++ and VBScript/VB on any given day.  I often find myself writing code in VB with semi-colons and C++ without them.  Also, I have become accustomed to some of the simple type conversion functions provided by VB such as CInt, CLng, CDbl, CStr.  To simplify my development I created companion functions in C++ to implement support for these functions (or a basic variant of these functions). Several of these functions just call other functions.  I decided to wrap these functions for the sole purpose of simplification.  These functions are listed below.  The function names and prototypes should be self explanatory.

CInt	int CInt(LPCTSTR lpszValue)
CLng	long CInt(LPCTSTR lpszValue)
CDbl	double CInt(LPCTSTR lpszValue)
CStrFromLong	CString CStrFromLong(const long lValue)
CStrFromInt	CString CStrFromInt(const int lValue)
CStrFromDouble	CString CStrFromDouble(const double dblValue)

Other General Functions

In addition to the equality operator and the type conversion operators I mentioned above, there are a few other functions I use quite often and have included here.  You may or may not need any of these functions, but if you do I think they will simplify your life.  These functions perform various operations and I am going to provide a description of each function to help you understand them.

BOOL CSomeWnd::PreTranslateMessage(MSG* pMsg) 
{
    if (::GetDlgCtrlId(pMsg->hwnd) == IDC_NUMERIC_CONTROL)
    {
        if (!ProcessKeyStrokeForNumeric(pMsg))
            return TRUE;
        }
           
    return CWnd::PreTranslateMessage(pMsg);
}      

BOOL CSomeWnd::PreTranslateMessage(MSG* pMsg) 
{
    if (::GetDlgCtrlId(pMsg->hwnd) == IDC_NUMERIC_CONTROL && 
        IsEditMsg(pMsg))
    return TRUE;

    return CWnd::PreTranslateMessage(pMsg);
}      

MFC Support/Requirement

As you've probably already noticed a couple of the functions I provide require MFC to work.  These use the CString class.  By default, support for these functions is not included.  To use these functions you need to define FPS_HELPER_MFC_SUPPORT somewhere appropriate in your code.  Many of you probably already have a favorite string class for your non-MFC projects.  Changing this code to use your favorite string class should be a very simple matter. 

How to Use These Functions In Your Application

There are 2 files included with this article.  The first step is to add these 2 files (HelperFunctions1.h and HelperFunctions1.cpp) to your project.  Once you have added these files to your project you need to include the HelperFunctions.h file in an appropriate place.  I typically include this file in my stdafx.h file so that my entire project has access to these functions without more coding.