C++11 introduced new forms of literals using modified syntax and semantics to provide User-Defined Literals (UDL) also known as Extensible Literals. While there was the ability to use them the standard library did not use any of them. In C++14, the commission added some standard literals. In this post, we explain user-defined literals operators and we explain some of these standard literals added in C++14.

What are the user defined literal operators in C++?

C++11 introduced new forms of literals using modified syntax and semantics in order to provide User-Defined Literals (UDL) also known as Extensible Literals. Using user-defined literals, user-defined classes can provide new literal syntax and they can be used with the operator "" to combine values with conversion operators. Here below, we explain how to use user-defined literals in C++.

What are the standard user-defined literals in C++14?

In C++14, we have some standard user-defined literal operators that comes with standard library. These are literals for basic strings, for chrono types, and for complex number types.

We can access to these operators by:

• using namespace std::literals;
• using namespace std::string_literals;
• using namespace std::literals::string_literals;

C++14 adds the following standard literals below,

For the string types there is an operator”” s() for basic string,

• s : std::basic_string types for creating the various string types std::string, std::wstring, etc.

here how we can use it with auto,

Suffixes for std::chrono::duration values,

• h : hour type for the std::chrono::duration time intervals
• m : minute type for the std::chrono::duration time intervals
• s : second type for the std::chrono::duration time intervals
• ms : millisecond type for the std::chrono::duration time intervals
• ns : nanosecond type for the std::chrono::duration time intervals
• us : u.second type for the std::chrono::duration time intervals

here how we can use them with auto,

Suffixes for complex number literals,

• if : imaginary number for the std::complex types
• i : imaginary number for the std::complex types
• il : imaginary number for the std::complex types

here how we can use them with auto,

there are more definitions.

Is there a full example of how to use standard user-defined literals in C++14?

Here is a full example about standard user-defined literals in C++.

For more information about the standard user-defined literals, please see https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3402.pdf

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