How to Achieve Precise Floating-Point Formatting with std::ostream?

Formatted Output of Floating-Point Values Using std::ostream

Question:

How can I achieve precise control over the formatting of floating-point values using std::ostream, similar to the printf_s function shown below?

<code class="cpp">printf_s("%11.6lf", my_double); // Prints " 42.000000"</code>

Answer:

To format floating-point values with std::cout, utilize stream manipulators. The following code achieves the desired output:

<code class="cpp">std::cout << std::fixed << std::setw(11) << std::setprecision(6) << my_double;</code>

Explanation:

• std::fixed: Specifies that the value should be formatted with a fixed number of decimal places.
• std::setw(11): Defines the minimum field width to which the value is padded with spaces.
• std::setprecision(6): Sets the number of decimal places to be displayed.
• std::setfill('0'): (Optional) Fills empty spaces with the specified character ('0' in this case).

Additional Resources:

For comprehensive documentation on std::ostream formatting, refer to the following resources:

• [std::ostream formatting](https://en.cppreference.com/w/cpp/io/manipulators) on cppreference.com
• [std::ostream](https://www.learncpp.com/cpp-tutorial/formatted-output-with-io-manipulators/) on learncpp.com

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