Header File in C++17

The <charconv> header contains several methods for converting character sequences to numerical information and vice versa. It is regarded as more effective than the <cstdlib> header file functions for the identical purpose. The functions given by the <charconv> header file are often quicker than the functions that are provided by the <cstdlib> header file.

It was introduced in C++17, and the major goal of developing this header was to enhance the complexity and speed of the code.

Functions in the <charconv> Header:

The charconv library has two functions:

1. to_chars()

The to_chars() method converts a number to its matching character representation and puts the output in a buffer.

Syntax:

It has the following syntax:

Parameters:

initial and final: Pointers to the start and end of the buffers where the output is going to be written.

val: The numeric value to be transformed.

Return Value:

It returns an object of type to_chars_result with two members:

ptr: a reference to the first character following the end reference of the characters typed.
ec: It is an error number that determines whether or not the process of conversion is completed. If the conversion succeeds, the code that indicates the problem will be set to errc; otherwise, it will be set to a different error code if an error occurs.

Example:

This code shows how to use the to_chars() method from the <charconv> header to convert a value of integers to a character sequence.

Filename: Tochars. cpp

// Program to implement the use of to_chars() method
#include <array> 
#include <charconv> 
#include <iostream> 
using namespace std; 
int main() 
{ 
	// the buffer value for storing
	array<char, 10> buffer; 
	// the int variable to convert
	int value = 44; 

	// integer to character sequence conversion
	auto res = to_chars( 
		buffer.data(), buffer.data() + buffer.size(), value); 

	// condition
	if (res.ec == errc()) { 
		// If successful, print the converted value 
		cout << "The Converted value: "
			<< string_view(buffer.data(), 
							res.ptr - buffer.data()) 
			<< endl; 
	} 

	return 0; 
}

Output:

The Converted value: 44

2. the function from_chars()

The from_chars() method is used for converting a number's character representation to its numeric form.

Parameters:

initial and final: Indicates the start and end of the character to be transformed.
value: The number that is to be converted's reference.

Return on Value

It returns the from_chars_result object, which has two members:

ptr: A pointer to the initial character following the last character entered it.
ec: It is an error code that indicates whether or not the conversion was successful. If the process of conversion is successful, the error code is going to be set to errc; otherwise, if an error occurs, it will be set to an error code.

Example:

Filename: Fromchars.cpp

// the program to implement from_chars() function in c++
#include <charconv> 
#include <iostream> 
using namespace std; 

int main() 
{ 
	// declaration of the string variable
	string st = "48"; 

	// variable for storing the converted value
	int value; 

	// function calling from_chars() 
	auto res = from_chars(st.data(), 
							st.data() + st.size(), value); 

	// condition to check the conversion
	if (res.ec == errc()) { 
		// If it is successful, then display the va;ue
		cout << value << endl; 
	} 

	return 0; 
}

Output:

Example 2:

Filename: Header.cpp

// the program to implement from_chars() function in c++
#include <charconv> 
#include <iostream> 
using namespace std; 
int main() 
{ 
	// user input string value
	string st = "126.78"; 
	// variable for storing the converted value
	double val = 0.0; 

	// Converting the string to a double value with std::from_chars The converted value is kept in 'val' 
	// 'ptr' is a reference to the character that appears in the string 
	// that comes after the converted value 'ec' is an error code that shows whether or not the conversion process was successful. 
	auto [ptr, ec] = from_chars( 
		st.data(), st.data() + st.size(), val); 

	// If no error occurs
	if (ec == errc{}) { 

		// display of the converted value
		cout << "The Converted value is: " << val << endl; 
	} 
	// If an error occurs
	else { 

		//display of the error code
		cout << "The Conversion is failed with an error code.?
			<< static_cast<int>(ec) << endl; 
	} 

	return 0; 
}

Output:

The Converted value is: 126.78

Benefits of Using <charconv> function

The following are some of the benefits of utilizing the <charconv> library functions in C++:

Performance: This header contains a large number of common functions that reduce memory allocation and increase code performance.
Error handling: It returns the from_chars_result, which indicates if the conversation was successful or not.
Flexibility: It can handle a large variety of input types and assures the code's adaptability.

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