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C++ Program for Double to String Conversion

Converting between data types is frequently required in C++. Converting a double-precision floating point number to a string representation is a common scenario. It allows displaying the double value to the user or printing it for debugging purposes. A double is a data type in C++ that has double precision for floating point numbers. It can accurately represent a wide range of values and is typically 64-bit wide.

An object representing a string of characters is called a string in C++. The standard string class in C++ is called std::string. Strings offer a convenient way to work with text and are frequently used to display data to users.

A double can be converted to a string to show the numerical value as text. We can use this to write the double to a file, web page, GUI, console, or anywhere else. The C++ standard library includes several methods for converting a double to a string with formatting control.

This article covers various methods for converting a double to a string in C++. It will explain what are double and String, and also demonstrate code examples for converting using std::to_string(), string streams, sprintf(), and controlling the precision. The critical methods provided by C++ to convert doubles to readable strings flexibly will be covered.

Approaches to Convert Double into String

Here are the main approaches to convert a long to a string in C++ without code examples:

  • Using to_string
  • The stringstream method
  • Applying sprintf
  • lexical_cast can be used.

The key is that C++ provides flexible options to convert a long integer to a readable string representation. The best choice depends on factors like the C++ version and the need for custom formatting.

Approach 1: to_string Method

In C++, the std::to_string Method converts numeric values to string representations. Here is a basic introduction to std::to_string:

  • It is declared by the <string> header file.
  • The to_string is a utility function that converts numeric types like int, long, double, etc. into a std::string.
  • It handles formatting the number into a string for you.


The syntax is very straightforward:

  • Where value is the number, you want to convert.
  • It returns the string version of the number.
  • No need to worry about character buffers, sprintf, streams, etc.
  • It is much simpler and safer than C-style conversion functions.
  • It handles floating-point types like double with full precision.
  • Overloads allow passing both integers and floats.
  • Available in C++11 and higher.


Let's take a C++ Program to convert 'double' into String using the 'to_string' Method.


Double: 3.14159
Long: 12345


This program first declares a double and long variable. After that, it uses std::to_string to convert each variable to a std::string.

The strings are printed out to demonstrate the conversion. It shows how to_string() can cleanly convert floating point and integer types to string representations.

The key points are:

  • Include <string> for std::string and to_string().
  • Use to_string() to convert variables to strings.
  • It can handle double and long data types.
  • Print or use strings for output.

It provides a simple example of using C++'s std::to_string functionality to format numeric types as strings within a complete program. The same technique can be applied to any data that needs conversion to String.

Approach 2: Using stringstream() Method:

The stringstream class in C++ provides a simple way to convert different data types to and from strings. Here is a brief introduction to stringstreams:

  • Stringstreams are declared in the <sstream>
  • They allow you to read and write from a string buffer as you would with cin and cout streams.

To use:

  • Construct a stringstream object.
  • Write data into the stringstream using <<
  • Call .str() to get the string contents
  • Stringstreams can accept inserts of many data types like int, double, String, bool, etc.
  • The contents can be extracted in various formats as well.
  • It allows building up strings from mixed data like printf-style formatting.
  • It provides type safety and avoids buffer overruns.
  • It allows you to convert string representations back into native data types.
  • It gives more flexibility and control than std::to_string().
  • It is useful for tasks like parsing, formatting, and converting data.


Let's take a C++ program to convert a 'double' into a string using std::stringstream.


Double: 3.24159


This example converts the double value 3.24159 to a string using std::stringstream. The generated String is then output to the console. The << operaString is used to stream the double value into the std::stringstream, and ss.str() is used to retrieve the content of the stringstream as a string.

Approach 3: Using sprintf Method:

The sprintf function allows converting a double data type to a string in C++. It takes the target string, formatting specifiers like %f, and the double value to convert as arguments. If you want to convert a double to a string, call sprintf, passing the target string, "%f" as the formatting specifier, and the double variable. The sprint() function will handle formatting the double and storing the resulting String. It provides a simple way to get a string vesting of a double for output or string processing.


Let's take a C++ Program to convert Double into String using the 'sprint' Method.


Double: 3.14159


In this example, the double value 3.14159 is converted to a string using the sprint() function. The format specifier "%.5f" is used to specify the precision (number of decimal places) in the conversion. After that, the generated String is printed to the console.

Approach 4: Using lexical_cast Method:

The lexical_cast template function from Boost provides a simple way to convert between data types in C++. If you want to convert a double to a string, include boost/lexical_cast.hpp and call lexical_caststd::string(double_value), passing the double variable to convert as the argument. The lexical_cast method handles conversion between data types, including to and from strings transparently. It will return a std::string containing the string representation of the double. It makes converting a double to a properly formatted string for further processing or output in C++ convenient with just one line and no need to manage formatting manually.


Let's take a C++ Program to convert Double into String using lexical_cast.


The converted String from double is: 7.89012


In this example, boost::lexical_cast converts the double value 7.89012 to a string. After that, the generated string is written to the console. Remember that to 'boost::lexical_cast', your development environment must have the Boost library set up and functioning correctly.

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