CPerlString - A Class to Utilize Perl String Functions

Thursday Mar 6th 2003 by Yap Chun Wei
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String manipulation and regular expressions have always been a strength of Perl. Here are two classes that encapsulate some of Perl's most useful string functions for C++. (The source code was updated.)



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Environment: VC++ 5.0-6.0, NT 4.0, Win2000, WinXP, Win95/98

String manipulation and regular expressions have always been a strength of Perl. The C language is powerful, but doing string manipulation and regular expressions is difficult. Although there are libraries such as PCRE that simulate Perl regular expressions in C, I have found them difficult to use. So, I thought, the best way is to embel Perl inside C.

With the help of Perl's documentation, I have successfully created two classes to encapsulate some of Perl's most useful functions. One class is for MFC users (CPerlString.h), and one class is for non-MFC users (PerlString.h). The functions encapsulated are:

  1. Pattern matching
  2. String substitution
  3. Joining of an array into a string
  4. Splitting of a string into an array
  5. Sort (forward or reverse)
  6. Chop
  7. Chomp

I will discuss the usage of the MFC class. The non-MFC class is similar but it uses STL string and vector<string> instead of CString and CStringArray.

I32 CPerlString::Match (CString inputString, CString pattern)
I32 CPerlString::Matches (CString inputString, CString pattern, CStringArray &matchList)

Match and Matches are two functions that make use of Perl's pattern-matching ability. Basically, Match sends a Perl statement: inputString =~ pattern and Matches sends a Perl statement: matchList = (inputString =~ pattern). Match will return 1 if the pattern is found and 0 if the pattern is not found. Matches will return the number of matches.

CPerlString perl;
CString inputString = "Hello World!";
CString pattern1 = "/Hello/";
CString pattern2 = "/(.o)/g";
CStringArray matchList;

if (perl.Match(inputString, pattern1))
  printf("Pattern found\n");
else
  printf("Pattern not found\n");

int num_matches = perl.Matches(inputString, pattern2, matchList);

printf("%d matches\n", num_matches);
if (num_matches > 0)
{
  for (int i = 0; i < matchList.GetSize(); i++)
    printf("Match %d: %s\n", i+1, matchList.GetAt(i));

I32 Substitute(CString &inputOutputString, CString pattern)

Substitute is a function that makes use of Perl's string substitute ability. Basically it sends: inputOutputString =~ pattern. Substitute will return 1 if the substitution is done and 0 if it is not done.

CPerlString perl;
CString inputOutputString = "Hello World!";
CString pattern1 = "s/Hello/Hello Happy/";

perl.Substitute(inputOutputString, pattern1);
printf("%s\n", inputOutputString);

void Join(CStringArray &inputStringList, CString pattern, CString &outputString)

Join is a function that makes use of Perl's joining ability. It sends: outputString = join (pattern, inputStringList). Join does not return any value.

CPerlString perl;
CString outputString;
CString pattern1 = " ";
CStringArray inputStringList;
inputStringList.Add("Hello");
inputStringList.Add("Happy");
inputStringList.Add("World");

perl.Join(inputStringList, pattern1, outputString);
printf ("%s\n", outputString);

I32 Split(CString inputString, CString pattern, CStringArray &splitList)

Split performs the Perl statement: splitlist = split (pattern, inputString). It returns the number of split items.

CPerlString perl;
CString inputString = "Hello Happy World!";
CString pattern1 = "/\\s/";
CStringArray splitList;

int num_split = perl.Split(inputString, pattern1, splitList);

printf("%d split\n", num_split);
if (num_split > 0)
{
  for (int i = 0; i < splitList.GetSize(); i++)
    printf("Split %d: %s\n", i+1, splitList.GetAt(i));

void Sort(CStringArray &inputStringList, CStringArray &outputStringList, int Direction = 0)

Sort performs sorting on an array by sending: outputStringList = sort (inputStringList) if the direction is 0 and outputStringList = reverse sort (inputStringList) if the direction is not 0 (for example, 1). Sort does not return any value.

CPerlString perl;
CStringArray inputStringList, outputStringList;
inputStringList.Add("Hello");
inputStringList.Add("Happy");
inputStringList.Add("World");

perl.Sort(inputStringList, outputStringList);    // Forward sort

for (int i = 0; i < outputStringList.GetSize(); i++)
  printf("%s\n", outputStringList.GetAt(i));

perl.Sort(inputStringList, outputStringList, 1); // Reverse sort

for (int i = 0; i < outputStringList.GetSize(); i++)
  printf("%s\n", outputStringList.GetAt(i));

void Chomp(CString &inputOutputString)
void Chomp(CStringArray &inputOutputStringList)
void Chop(CString &inputOutputString)
void Chop(CStringArray &inputOutputStringList)

Chop and Chomp are two functions that perform Perl's chop and chomp. They are overloaded to handle a string and a string array. The corresponding Perl statement is: chomp (inputOutputString) or chomp (inputOutputStringList) or chop (inputOutputString) or chop (inputOutputStringList).

CPerlString perl;
CString inputOutputString = "Hello World!";
CStringArray inputOutputStringList;
inputOutputStringList.Add("Hello");
inputOutputStringList.Add("Happy");
inputOutputStringList.Add("World");

perl.Chop(inputOutputString);
printf("%s\n", inputOutputString);

perl.Chop(inputOutputStringList);
for (int i = 0; i < inputOutputStringList.GetSize(); i++)
  printf("%s\n", inputOutputStringList.GetAt(i));

Usage:

To use the two classes, you will need to include them in your project by adding the statement: #include "CPerlString.h" or #include "PerlString.h". You will also need to have the Perl core libraries. These will be found in the directory where you install Perl. For example, if you install Perl in C:\Perl, the core libraries will be found at C:\Perl\lib\CORE. You will need to set this directory as one of the default include and library directories for Visual C++. This can be done by choosing Tools->Options->Directories and adding C:\Perl\lib\CORE in the include files and library files section.

Demo

The demo program demonstrates the use of the above-mentioned functions except chomp and chop. It can be used to help test your regular expression patterns.

Downloads

Download demo project - 40 Kb
Download source - 4 Kb
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