cxxo-utils.hpp File Reference

Small utilities used by various components of cxxomfort, but low-level and generic enough that they don't get categorized into the backport headers. More...

Classes
struct	noop_t
	noop function More...
class	outp< T >
	denotes a reference used as an output argument to a function. More...
struct	prio< I >
	priority tag struct, for ordering of function specializations. More...
struct	constexpr_t
	Tag type for constexpr. More...
struct	OpaqueNative< Ty, Tag >
	Wraps and tags a native C type as an opaque type. More...

Namespaces
	cxxomfort
	Namespace of the cxxomfort library.

Typedefs
typedef rvoid	None_t

Functions
template<typename T >
CXXO_CONSTEXPR T	min (constexpr_t, T a, T b) CXXO_NOEXCEPTNOTHROW
template<typename T >
CXXO_CONSTEXPR T	max (constexpr_t, T a, T b) CXXO_NOEXCEPTNOTHROW
bool	bool_once (bool &flag) CXXO_NOEXCEPTNOTHROW
	Evaluates a bool variable and "unchecks" it, returnnig its old value. More...
template<typename T >
T const *	coalesce_ptrs (T *... ptrs) noexcept
	Examines a series of pointers and returns the value in the first non-NULL element among them. More...
template<typename Iter >
Iter	coalesce (Iter ini, Iter fin) CXXO_NOEXCEPTNOTHROW
	Coalesces a sequence, returning the first non-NULL element, or the last element. More...

Variables
const noop_t	noop
	noop functor - when evaluated with arguments, it does nothing

Detailed Description

Small utilities used by various components of cxxomfort, but low-level and generic enough that they don't get categorized into the backport headers.

Utilities:

Header File

#include <cxxomfort/cxxo-utils.hpp>

Including this header brings up the base cxxomfort utilities as well.

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Class Documentation

cxxomfort::constexpr_t

struct cxxomfort::constexpr_t

Tag type for constexpr.

This is used by some cxxomfort utilities to disambiguate provided function calls that only differ on whether they can work in constexpr context.

cxxomfort::OpaqueNative

struct cxxomfort::OpaqueNative

template<typename Ty, typename Tag>
struct cxxomfort::OpaqueNative< Ty, Tag >

Wraps and tags a native C type as an opaque type.

See also

https://nullptr.nl/2018/02/phantom-types/

OpaqueNative takes a native C type, like int or float and wraps it with a Tag type as an opaque (named) type. The result is a type that can be used by explicitly accessing the underlying type where desired.

The wrapper provides access to the underlying object via the value member, but the opaque interface is used via the value() and opaque() functions.

typedef OpaqueNative<double, height_tag> Height;
typedef OpaqueNativ<unsigned, age_tag> Age;

Handle_type match_person (string name, Height h, Age a) { ... }

match_person("John Doe", 32, 33); // fails
match_person("John Doe", opaque<Height>(32), opaque<Age>(33) ); // works
match_person("John Doe", opaque<Age>(33), opaque<Age>(33) ); // fails