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Namespace Subspace :: sus :: construct

Concepts and functions for constructing and converting between types.

Type conversions

This namespace provides tools for three general methods of converting between types:

  • Infallible conversions which preserve values: From / Into
  • Fallible conversions which preserve values or fail explicitly: TryFrom / TryInto
  • Infallib;e conversions which can change values or lose data: Cast

Usually prefer to convert between types with the value-preserving methods of From and Into and TryInto when possible. Cast is required for converting from floating point to integer values, and from larger integer types to floating point, as these are lossy conversions.

The into function allows explicit conversion while deducing the target type, such as for converting function arguments or return values.

Concept Usage Infallible Preserves values
From / Into T::from(x) / sus::into(x) ✅ ✅
TryFrom / TryInto T::try_from(x) / sus::try_into<T>(x) ❌ ✅
Cast sus::cast<T>(x) ✅ ❌

See Cast for how numeric and primitive values are converted with cast.

Default construction

The Default concept matches types which can be default constructed, allowing their use in generic code.

Constructing from and holding references

The SafelyConstructibleFromReference concept pairs with the [[clang::lifetimebound]] attribute, which gives better protection with Clang. The concept can be used in generic code that accepts reference types to prevent receiving references to implicit temporary objects in a standard way.

Classes

Functions

  • cast

    An infallible conversion (cast) that may lose the original value in the process.

  • into

    Converts from the given value to whatever a receiver requires.

  • move_into

    Moves from and converts from the given value to whatever a receiver requires.

  • try_into

    Attempts to convert from the given value to a ToType.

Concepts

  • Cast

    When a pair of types T and F satisfy Cast<T, F>, it means that F can be cast to T through a conversion that will always succeed in producing some value, but may be lossy or produce a value with a different meaning. The conversion may truncate or extend F in order to do the conversion to T.

  • Default

    Default types are able to be constructed with a default value.

  • From

    A concept that indicates ToType can be constructed from a FromType, via ToType::from(FromType).

  • Into

    A concept that declares FromType can be converted to ToType.

  • SafelyConstructibleFromReference

    Returns whether a type From is safely constructible from a reference of type To. If To is a const reference, then the types must match, as a conversion would create a reference to a temporary.

  • TryFrom

    A concept that indicates ToType can be (sometimes) constructed from a FromType, via ToType::try_from(FromType).

  • TryInto

    A concept that declares FromType can (sometimes) be converted to ToType through the TryFrom concept or through an identity transformation.