celeritas::OpaqueId< ItemT, SizeT > Class Template Reference

Type-safe index for accessing an array or collection of data. More...

#include <OpaqueId.hh>

Public Types
Type aliases
using	value_type = ItemT
using	size_type = SizeT

Public Member Functions
constexpr	OpaqueId ()
	Default to null state.
constexpr	OpaqueId (size_type index)
	Construct explicitly with stored value.
constexpr	operator bool () const
	Whether this ID is in a valid (assigned) state.
OpaqueId &	operator++ ()
	Pre-increment of the ID.
OpaqueId	operator++ (int)
	Post-increment of the ID.
OpaqueId &	operator-- ()
	Pre-decrement of the ID.
OpaqueId	operator-- (int)
	Post-decrement of the ID.
size_type	get () const
	Get the ID's value.
constexpr size_type	unchecked_get () const
	Get the value without checking for validity (atypical)
constexpr size_type const *	data () const
	Access the underlying data for more efficient loading from memory.

Detailed Description

template<class ItemT, class SizeT = ::celeritas::size_type>
class celeritas::OpaqueId< ItemT, SizeT >

Type-safe index for accessing an array or collection of data.

Template Parameters

ItemT	Type of an item at the index corresponding to this ID
SizeT	Unsigned integer index

It's common for classes and functions to take multiple indices, especially for O(1) indexing for performance. By annotating these values with a type, we give them semantic meaning, and we gain compile-time type safety.

If this class is used for indexing into an array, then ValueT argument should usually be the value type of the array: Foo operator[](OpaqueId<Foo>)

An OpaqueId object evaluates to true if it has a value, or false if it does not (a "null" ID, analogous to a null pointer: it does not correspond to a valid value). A "true" ID will always compare less than a "false" ID: you can use std::partition and erase to remove invalid IDs from a vector.

See also id_cast below for checked construction of OpaqueIds from generic integer values (avoid compile-time warnings or errors from signed/truncated integers).

Todo:

This interface will be changed to be more like std::optional : size_type will become value_type (the value of a 'dereferenced' ID) and operator* or value will be used to access the integer.

---

The documentation for this class was generated from the following file:

• OpaqueId.hh