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STL split string function

, 13 May 2007
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Split a string using a single character delimiter. Template function.

Introduction

Splitting a string using a given delimiter is a very common operation.
Unfortunately the STL doesn't provide any direct way to achieve this.
This split implementation is templatised and uses type deduction to determine what kind of string and container are being passed as arguments, which must must be some form of basic_string<> and any container that implements the push_back() method.

You may either place this code directly into the file where it is used, or create a separate include file for it.

Note that the string type is not fully specified, allowing the traits and allocator to default.
In some situations this may not be what you want and some compilers might not like it.

Background

I wrote this when I found that the code written by Paul J. Weiss with the title STL Split String was more complex than I needed for this common simple case.

The most common case should be the easiest to write.

Source Code

template <typename E, typename C>
size_t split(std::basic_string<E> const& s,
             C &container,
             E const delimiter,
             bool keepBlankFields = true)
{
    size_t n = 0;
    std::basic_string<E>::const_iterator it = s.begin(), end = s.end(), first;
    for (first = it; it != end; ++it)
    {
        // Examine each character and if it matches the delimiter
        if (delimiter == *it)
        {
            if (keepBlankFields || first != it)
            {
                // extract the current field from the string and
                // append the current field to the given container
                container.push_back(std::basic_string<E>(first, it));
                ++n;
                
                // skip the delimiter
                first = it + 1;
            }
            else
            {
                ++first;
            }
        }
    }
    if (keepBlankFields || first != it)
    {
        // extract the last field from the string and
        // append the last field to the given container
        container.push_back(std::basic_string<E>(first, it));
        ++n;
    }
    return n;
}

Example Usage

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>

std::string tests[3] = {
    std::string(""),
    std::string("||three||five|"),
    std::string("|two|three||five|")
};

char* delimiter = "|";

for (int i = 0; i < sizeof(tests)/sizeof(tests[0]); ++i)
{
    std::vector< std::basic_string<char> > x;
    size_t n = split(tests[i], x, delimiter[0], true);
    std::cout << n << "==" << x.size() << " fields" << std::endl;
    if (n)
    {
        std::copy(x.begin(), x.end(),
            std::ostream_iterator<std::string>(std::cout, delimiter));
        std::cout << std::endl;
    }
}

License

This article, along with any associated source code and files, is licensed under A Public Domain dedication

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About the Author

David 'dex' Schwartz
Team Leader
Australia Australia
Developing various kinds of software using C/C++ since 1984 or so. Started out writing 8086 asm for direct screen i/o and mouse handling etc.
Used several other languages eg. Java, Python, Clipper/dBase, FORTRAN 77, Natural ADABAS, Unix scripting, etc.
My current work involves Enterprise Content Management on Win32.

Comments and Discussions

 
QuestionQuick split using vector as base class PinmemberDennis Lang21-Feb-12 10:25 
GeneralCan't compile in GCC 4.40. Pinmemberscmeiqy6-Dec-09 0:15 
GeneralRe: Can't compile in GCC 4.40. PinmemberDavid 'dex' Schwartz7-Dec-09 21:58 
GeneralRe: Can't compile in GCC 4.40. PinmemberDavid 'dex' Schwartz8-Dec-09 0:13 
Generalpush_back PinmemberPablo Aliskevicius9-Apr-07 21:17 
AnswerRe: push_back PinmemberDavid 'dex' Schwartz12-May-07 4:52 
GeneralBoost String Algorithms PinmemberGast1287-Apr-07 21:25 
GeneralRe: Boost String Algorithms PinmemberGarth J Lancaster7-Apr-07 22:05 
GeneralRe: Boost String Algorithms PinmemberGast1287-Apr-07 22:54 
The string algo is completely template based and works with the concept of sequences and ranges like strings. There are boost libraries which requires DLL's to be built (e.g. regex, filesystem, serialization, program options), but if you don't need them, you don't use them.
GeneralRe: Boost String Algorithms PinmemberVirtual Coder8-Apr-07 9:57 
GeneralRe: Boost String Algorithms PinmemberDavid 'dex' Schwartz8-Apr-07 12:49 
GeneralRe: Boost String Algorithms PinmemberGast1288-Apr-07 22:02 
GeneralRe: Boost String Algorithms PinmvpStephen Hewitt13-May-07 15:18 
GeneralRe: Boost String Algorithms PinmemberJohn M. Drescher14-May-07 20:44 
GeneralRe: Boost String Algorithms PinmvpStephen Hewitt15-May-07 13:59 
GeneralRe: Boost String Algorithms PinmemberJohn M. Drescher15-May-07 14:11 
GeneralRe: Boost String Algorithms PinmvpStephen Hewitt15-May-07 14:13 
GeneralRe: Boost String Algorithms PinmemberJohn M. Drescher15-May-07 15:47 

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