How can I trim and reduce strings in C ?

Trimming and Reducing Strings in C

Trimming and reducing strings are common operations in programming. Trimming refers to removing leading and trailing whitespace characters from a string, while reducing involves replacing consecutive whitespace characters with a single predefined character or string.

Trimming Strings

To trim a string in C , you can use the find_first_not_of and find_last_not_of methods to identify the first and last non-whitespace characters. The code below illustrates this approach:

#include <string>

std::string trim(const std::string& str) {
    const auto strBegin = str.find_first_not_of(" \t");
    if (strBegin == std::string::npos)
        return ""; // no content

    const auto strEnd = str.find_last_not_of(" \t");
    const auto strRange = strEnd - strBegin + 1;

    return str.substr(strBegin, strRange);
}

Reducing Strings

Reducing a string involves replacing consecutive whitespace characters with a predefined character or string. Here's a function that performs this operation:

std::string reduce(const std::string& str, const std::string& fill = " ", const std::string& whitespace = " \t") {
    // trim first
    auto result = trim(str);

    // replace sub ranges
    auto beginSpace = result.find_first_of(whitespace);
    while (beginSpace != std::string::npos) {
        const auto endSpace = result.find_first_not_of(whitespace, beginSpace);
        const auto range = endSpace - beginSpace;

        result.replace(beginSpace, range, fill);

        const auto newStart = beginSpace + fill.length();
        beginSpace = result.find_first_of(whitespace, newStart);
    }

    return result;
}

Example Usage

Here's an example demonstrating the usage of the trim and reduce functions:

const std::string foo = "    too much\t   \tspace\t\t\t  ";
const std::string bar = "one\ntwo";

std::cout << "[" << trim(foo) << "]" << std::endl;
std::cout << "[" << reduce(foo) << "]" << std::endl;
std::cout << "[" << reduce(foo, "-") << "]" << std::endl;

std::cout << "[" << trim(bar) << "]" << std::endl;

Output

[too much               space]  
[too much space]  
[too-much-space]  
[one  
two]

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