How to Convert Float to String with Precision and Decimal Digits Specified in C ?

Convert Float to String with Precision and Decimal Digits Specified

Converting a float to a string in C while specifying the precision and number of decimal digits is often necessary for formatting numerical data.

One common approach is to utilize stringstream:

<code class="cpp">#include <sstream>

double pi = 3.14159265359;
std::stringstream stream;
stream << std::fixed << std::setprecision(2) << pi;
std::string s = stream.str();

The fixed manipulator ensures fixed-point notation, while setprecision(2) limits the decimal part to two digits.

C 17 introduced the to_chars function for technical conversions:

<code class="cpp">#include <array>
#include <charconv>

double pi = 3.14159265359;
std::array<char, 128> buffer;
auto [ptr, ec] = std::to_chars(buffer.data(), buffer.data() + buffer.size(), pi,
                               std::chars_format::fixed, 2);
if (ec == std::errc{}) {
    std::string s(buffer.data(), ptr);
}</code>

Remember to ensure compiler compliance when using to_chars.

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