reflection

Module nu.core.reflection.

Reflection atoms: Python's introspection builtins.

Maps Python's builtins that inspect a value's type, identity, or shape onto Nu ScalarQueries. Pure compute; no Context effect of their own.

Builtins covered (Python -> Nu):

type / class: type -> Type, isinstance -> IsInstance, issubclass -> IsSubclass, callable -> Callable
identity / value: id -> Id, hash -> Hash
namespace: dir -> Dir, vars -> Vars

Sorts: all ScalarQuery (Q). Type, Callable, Id, Hash, Dir and Vars are unary. IsInstance and IsSubclass are binary (value, class). Dir and Vars yield a collection but are scalar builders (one list / dict), not streams.

Each atom defines compile (sync hot path) and acompile (async hot path). Both return a thunk (rt) -> value (sync) or (rt) -> awaitable (async) that captures the precompiled child thunks, so recursion skips the Runtime.eval / Runtime.aeval dispatch hop per child. Sentinel propagation is inlined: an EMPTY or INVALID operand collapses the result to INVALID without inspecting.

OOP descriptors (super, object, property, classmethod, staticmethod, memoryview) are not in this pass. They go to extensions later, once the OOP descriptor surface is designed.

Name	Sort	Call	Meaning
Callable	`scalar_query`	`Callable(value)`	Whether its one child appears callable (`callable`).
Dir	`scalar_query`	`Dir(value)`	The sorted attribute-name list of its one child (`dir`).
Hash	`scalar_query`	`Hash(value)`	The hash of its one child (`hash`).
Id	`scalar_query`	`Id(value)`	The identity of its one child (`id`).
IsInstance	`scalar_query`	`IsInstance(value, klass)`	Whether the first child is an instance of the second (`isinstance`).
IsSubclass	`scalar_query`	`IsSubclass(cls, klass)`	Whether the first child is a subclass of the second (`issubclass`).
Type	`scalar_query`	`Type(value)`	The type of its one child (`type`).
Vars	`scalar_query`	`Vars(value)`	The `__dict__` of its one child (`vars`).

Callable

Whether its one child appears callable (callable).

Callable(value)

Path nu.core.Callable. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 1 (1 required).

Arguments

Name	Type	Default	Meaning
`value`			the value to check.

Yields

True or False. INVALID when the child is EMPTY or INVALID.

Notes

A true result is not a guarantee: an object can define __call__ and still fail when actually called, same as Python's callable.

Example

nu.run(nu.Callable(len))[0]

True

Dir

The sorted attribute-name list of its one child (dir).

Dir(value)

Path nu.core.Dir. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 1 (1 required).

Arguments

Name	Type	Default	Meaning
`value`			the value to inspect.

Yields

A sorted list of attribute names. INVALID when the child is EMPTY or INVALID.

Example

nu.run(nu.Dir(True))[0][:3]

['__abs__', '__add__', '__and__']

Hash

The hash of its one child (hash).

Hash(value)

Path nu.core.Hash. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 1 (1 required).

Arguments

Name	Type	Default	Meaning
`value`			the value to inspect.

Yields

An integer. INVALID when the child is EMPTY or INVALID.

Notes

Only hashable values work. An unhashable child raises, same as Python's hash, since that's a real error and not a sentinel.

Example

nu.run(nu.Hash("abc"))[0] == hash("abc")

True

Id

The identity of its one child (id).

Id(value)

Path nu.core.Id. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 1 (1 required).

Arguments

Name	Type	Default	Meaning
`value`			the value to inspect.

Yields

An integer unique to the object for its lifetime. INVALID when the child is EMPTY or INVALID.

Notes

In CPython the identity is the object's memory address for its lifetime, so it's only meaningful while the object stays alive.

Example

nu.run(nu.Id(5))[0] == id(5)

True

IsInstance

Whether the first child is an instance of the second (isinstance).

IsInstance(value, klass)

Path nu.core.IsInstance. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 2 (2 required).

Arguments

Name	Type	Default	Meaning
`value`			the value to check.
`klass`			the type, or tuple of types, to check against.

Yields

True or False. INVALID when either child is EMPTY or INVALID.

Notes

The right child is evaluated only after the left yields a value, so a sentinel on the left short-circuits without touching the right.

Example

nu.run(nu.IsInstance(5, int))[0]

True

IsSubclass

Whether the first child is a subclass of the second (issubclass).

IsSubclass(cls, klass)

Path nu.core.IsSubclass. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 2 (2 required).

Arguments

Name	Type	Default	Meaning
`cls`			the class to check.
`klass`			the type, or tuple of types, to check against.

Yields

True or False. INVALID when either child is EMPTY or INVALID.

Notes

The right child is evaluated only after the left yields a value, so a sentinel on the left short-circuits without touching the right.

Example

nu.run(nu.IsSubclass(bool, int))[0]

True

Type

The type of its one child (type).

Type(value)

Path nu.core.Type. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 1 (1 required).

Arguments

Name	Type	Default	Meaning
`value`			the value to inspect.

Yields

The value's type. INVALID when the child is EMPTY or INVALID.

Example

nu.run(nu.Type(5))[0]

<class 'int'>

Vars

The __dict__ of its one child (vars).

Vars(value)

Path nu.core.Vars. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 1 (1 required).

Arguments

Name	Type	Default	Meaning
`value`			the value to inspect.

Yields

A dict. INVALID when the child is EMPTY or INVALID.

Notes

Objects with no __dict__ (most builtins, __slots__-only classes) raise, same as Python's vars.

Example

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y
nu.run(nu.Vars(Point(1, 2)))[0]

{'x': 1, 'y': 2}

reflection

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