#include <string>
#include <string_view>
#include <fmt/format.h>

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Namespaces
	drake

Macros
#define	DRAKE_FMT8_CONST const
	When using fmt >= 8, this is defined to be `const` to indicate that the `fmt::formatter<T>::format(...)` function should be object-const. More...

#define	DRAKE_FORMATTER_AS(TEMPLATE_ARGS, NAMESPACE, TYPE, ARG, EXPR)
	Adds a `fmt::formatter<NAMESPACE::TYPE>` template specialization that formats the `TYPE` by delegating the formatting using a transformed expression, as if a conversion function like this were interposed during formatting: More...

Functions
auto	fmt_runtime (std::string_view s)
	When using fmt >= 8, this is an alias for fmt::runtime. More...

template<typename T >
std::string	fmt_floating_point (T x)
	Returns `fmt::to_string(x)` but always with at least one digit after the decimal point. More...

Macro Definition Documentation

◆ DRAKE_FMT8_CONST

#define DRAKE_FMT8_CONST const

When using fmt >= 8, this is defined to be const to indicate that the fmt::formatter<T>::format(...) function should be object-const.

When using fmt < 8, the function signature was incorrect (lacking the const), so this macro will be empty.

◆ DRAKE_FORMATTER_AS

#define DRAKE_FORMATTER_AS	(	TEMPLATE_ARGS,
		NAMESPACE,
		TYPE,
		ARG,
		EXPR
	)

Adds a fmt::formatter<NAMESPACE::TYPE> template specialization that formats the TYPE by delegating the formatting using a transformed expression, as if a conversion function like this were interposed during formatting:

template <TEMPLATE_ARGS>
auto format_as(const NAMESPACE::TYPE& ARG) {
  return EXPR;
}

For example, this declaration ...

DRAKE_FORMATTER_AS(, my_namespace, MyType, x, x.to_string())

... changes this code ...

MyType foo;

fmt::print(foo);

... to be equivalent to ...

MyType foo;

fmt::print(foo.to_string());

... allowing user to format my_namespace::MyType objects without manually adding the to_string call every time.

This provides a convenient mechanism to add formatters for classes that already have a to_string function, or classes that are just thin wrappers over simple types (ints, enums, etc.).

Always use this macro in the global namespace, and do not use a semicolon (;) afterward.

Parameters

TEMPLATE_ARGS	The optional first argument `TEMPLATE_ARGS` can be used in case the `TYPE` is templated, e.g., it might commonly be set to `typename T`. It should be left empty when the TYPE is not templated. In case `TYPE` has multiple template arguments, note that macros will fight with commas so you should use `typename... Ts` instead of writing them all out.
NAMESPACE	The namespace that encloses the `TYPE` being formatted. Cannot be empty. For nested namespaces, use intemediate colons, e.g., `drake::common`. Do not place leading colons on the `NAMESPACE`.
TYPE	The class name (or struct name, or enum name, etc.) being formatted. Do not place leading double-colons on the `TYPE`. If the type is templated, use the template arguments here, e.g., `MyOptional<T>` if `TEMPLATE_ARGS` was chosen as `typename T`.
ARG	A placeholder variable name to use for the value (i.e., object) being formatted within the `EXPR` expression.
EXPR	An expression to `return` from the format_as function; it can refer to the given `ARG` name which will be of type `const TYPE& ARG`.

Note: In future versions of fmt (perhaps fmt >= 10) there might be an ADL format_as customization point with this feature built-in. If so, then we can update this macro to use that spelling, and eventually deprecate the macro once Drake drops support for earlier version of fmt.

Namespaces

Macros

Functions

Macro Definition Documentation

◆ DRAKE_FMT8_CONST

◆ DRAKE_FORMATTER_AS