Class DTypeCasting

Namespace

NumSharp

Assembly

NumSharp.dll

The NEP 43 casting engine over descriptors — the ports of NumPy's convert_datatype.c entry points: GetCastingImpl(DTypeMeta, DTypeMeta) (PyArray_GetCastingImpl), GetCastInfo(DType, DType, DTypeMeta, out long) (PyArray_GetCastInfo), CheckCastSafety(NPY_CASTING, DType, DType, DTypeMeta) (PyArray_CheckCastSafety), CanCastTypeTo(DType, DType, NPY_CASTING) (PyArray_CanCastTypeTo — the engine behind np.can_cast), EquivTypes(DType, DType) (PyArray_EquivTypes), MinCastSafety(NPY_CASTING, NPY_CASTING) and the casting-string parser. Every question is answered by the CastingImpl registered for the CLASS pair, so a new dtype joins np.can_cast by registering its casts — no table edit.

public static class DTypeCasting

Inheritance

object

DTypeCasting

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

For the storage-backed builtins the answers are exactly those np.can_cast(NPTypeCode, NPTypeCode) always gave (the BuiltinCastingImpl encodes the same table + kind-order rules), which the dtype_text differential-fuzz tier gates. What is new is everything a table cannot express: byte order (can_cast('>i4', 'i4', 'equiv') is True, 'no' is False) and the datetime unit rules.

Methods

CanCastTypeTo(DType, DType, NPY_CASTING)

NumPy's PyArray_CanCastTypeTo — the engine behind np.can_cast(from, to, casting) for two descriptors. An impossible cast is False, never an error.

public static bool CanCastTypeTo(DType from, DType to, NPY_CASTING casting)

Parameters

from DType

to DType

casting NPY_CASTING

Returns

bool

CastingToString(NPY_CASTING)

NumPy's npy_casting_to_string: the casting string of a level.

public static string CastingToString(NPY_CASTING casting)

Parameters

casting NPY_CASTING

Returns

string

CheckCastSafety(NPY_CASTING, DType, DType, DTypeMeta)

NumPy's PyArray_CheckCastSafety: whether casting from to to (or to the class toMeta when to is null) satisfies casting. Short-circuits on the implementation's own minimal safety and only resolves descriptors when the request is stricter than that.

public static bool CheckCastSafety(NPY_CASTING casting, DType from, DType to, DTypeMeta toMeta)

Parameters

casting NPY_CASTING

from DType

to DType

toMeta DTypeMeta

Returns

bool

EquivTypes(DType, DType)

NumPy's PyArray_EquivTypes: two descriptors are equivalent when casting between them is a no-cast (same class and byte order; for datetimes also an exact metric-prefix fold such as M8[1000ms] → M8[s], which is why NumPy's == is not symmetric there — Equals(DType) is structural instead).

public static bool EquivTypes(DType type1, DType type2)

Parameters

type1 DType

type2 DType

Returns

bool

GetCastInfo(DType, DType, DTypeMeta, out long)

NumPy's PyArray_GetCastInfo: the cast safety between two descriptors (to may be null to ask about the class toMeta — "cast to whatever instance you pick"), plus the byte offset at which the cast is a plain view (NoView when it is not). Null when the cast is impossible (NumPy returns -1).

public static NPY_CASTING? GetCastInfo(DType from, DType to, DTypeMeta toMeta, out long viewOffset)

Parameters

from DType

to DType

toMeta DTypeMeta

viewOffset long

Returns

NPY_CASTING?

GetCastingImpl(DTypeMeta, DTypeMeta)

The casting implementation from one class to another, or null when no cast exists — PyArray_GetCastingImpl.

public static CastingImpl GetCastingImpl(DTypeMeta from, DTypeMeta to)

Parameters

from DTypeMeta

to DTypeMeta

Returns

CastingImpl

KindToOrdering(char)

NumPy's dtype_kind_to_ordering: the kind ordering behind same_kind casting — b(0) < u(1) < i(2) < f(4) < c(5) < S(6) < U(7) < V(8) < O(9); datetime kinds do not fit the hierarchy (-1).

public static int KindToOrdering(char kind)

Parameters

kind char

Returns

int

MinCastSafety(NPY_CASTING, NPY_CASTING)

NumPy's PyArray_MinCastSafety: the LESS safe of two cast levels (the enum is ordered no < equiv < safe < same_kind < unsafe, so the larger value wins).

public static NPY_CASTING MinCastSafety(NPY_CASTING casting1, NPY_CASTING casting2)

Parameters

casting1 NPY_CASTING

casting2 NPY_CASTING

Returns

NPY_CASTING

ParseCasting(string)

NumPy's PyArray_CastingConverter: the case-sensitive casting strings.

public static NPY_CASTING ParseCasting(string casting)

Parameters

casting string

Returns

NPY_CASTING

Exceptions

ValueError

casting must be one of 'no', 'equiv', 'safe', 'same_kind', 'unsafe' (got '…').