C++
#include <iostream>
#include <string>
#include <sstream>
#include <iomanip>
using namespace std;
int main() {
double num = 123.456;
// Method 1: Using to_string()
string str1 = to_string(num);
// Method 2: Using stringstream with precision
stringstream ss;
ss << fixed << setprecision(2) << num;
string str2 = ss.str();
cout << "Double: " << num << endl;
cout << "String (method 1): " << str1 << endl;
cout << "String (method 2): " << str2 << endl;
return 0;
}Output
Double: 123.456 String (method 1): 123.456000 String (method 2): 123.46
Convert Double to String in C++
This program teaches you how to convert a double (floating-point number) into a string in C++. This conversion is essential when you need to display decimal numbers as text, format output with specific precision, write numbers to files, or combine numbers with strings. Understanding different conversion methods, especially for controlling decimal precision, is crucial for professional output formatting.
What This Program Does
The program converts a double (like 123.456) into a string (like "123.456" or "123.46" with formatting). This conversion is necessary because:
- You need to combine decimal numbers with text in output
- File operations often require string format
- String manipulation functions work with strings, not doubles
- Display formatting requires precise control over decimal places
Example:
- Input double: 123.456
- Output string (basic): "123.456000" (default precision)
- Output string (formatted): "123.46" (2 decimal places)
Methods for Conversion
Method 1: Using to_string()
cppstring str1 = to_string(num);
- Simple method, but has limitations
- Default precision is typically 6 decimal places
- No control over formatting
- May show unnecessary trailing zeros
Method 2: Using stringstream with Precision
cppstringstream ss; ss << fixed << setprecision(2) << num; string str2 = ss.str();
- Recommended method for formatted conversion
- Full control over decimal precision
- Can format with fixed or scientific notation
- Professional output formatting
When to Use Each Method
-
to_string(): Simple cases where default precision is acceptable
-
stringstream with formatting: Best for most cases - full control over precision and format
Summary
- Converting doubles to strings is essential for output formatting and string operations.
- to_string() is simple but has limited formatting control (default 6 decimals).
- stringstream with fixed and setprecision is the recommended method for formatted output.
- Always use formatted precision for professional output, especially in financial applications.
This program is fundamental for beginners learning how to format decimal numbers, control output precision, and create professional-looking displays in C++ programs.