primitives.sentinel

Module nu.forms.primitives.sentinel_.

Sentinel interfaces - SentinelForm, EmptyForm, InvalidForm.

Wraps EMPTY and INVALID so they can appear as typed Form nodes in a Nu tree, mainly so is_empty() / is_invalid() have something typed to call on.

Name	Sort	Call	Meaning
EmptyForm	`scalar_query`	`EmptyForm()`	Wraps EMPTY, the address-resolved-to-nothing sentinel.
InvalidForm	`scalar_query`	`InvalidForm()`	Wraps INVALID, the operation-not-applicable sentinel.
SentinelForm	`scalar_query`	`SentinelForm()`	Base for the sentinel interfaces, EmptyForm and InvalidForm.

EmptyForm

Wraps EMPTY, the address-resolved-to-nothing sentinel.

EmptyForm()

Path nu.forms.EmptyForm. Kind ScalarQuery, sort scalar_query, cardinality scalar.

Example

nu.run(nu.EmptyForm())[0]

<EMPTY>

Inherited methods

From nu.lang.forms.Form:

Call	Builds	Meaning
`.is_empty()`	`Bool`	True if this Form yields the EMPTY sentinel.
`.is_invalid()`	`Bool`	True if this Form yields the INVALID sentinel.
`.is_sentinel()`	`Bool`	True if this Form yields either sentinel (EMPTY or INVALID).
`.not_empty()`	`Bool`	True if this Form does not yield EMPTY.
`.not_invalid()`	`Bool`	True if this Form does not yield INVALID.

Wraps INVALID, the operation-not-applicable sentinel.

InvalidForm()

Path nu.forms.InvalidForm. Kind ScalarQuery, sort scalar_query, cardinality scalar.

Notes

INVALID arises when an operation is applied to an EMPTY operand, and Query chains collapse to INVALID as soon as any operand is a sentinel. This Form does not produce that propagation itself, it just gives INVALID a typed node.

Example

nu.run(nu.InvalidForm())[0]

<INVALID>

Inherited methods

From nu.lang.forms.Form:

Call	Builds	Meaning
`.is_empty()`	`Bool`	True if this Form yields the EMPTY sentinel.
`.is_invalid()`	`Bool`	True if this Form yields the INVALID sentinel.
`.is_sentinel()`	`Bool`	True if this Form yields either sentinel (EMPTY or INVALID).
`.not_empty()`	`Bool`	True if this Form does not yield EMPTY.
`.not_invalid()`	`Bool`	True if this Form does not yield INVALID.

Base for the sentinel interfaces, EmptyForm and InvalidForm.

SentinelForm()

Path nu.forms.SentinelForm. Kind ScalarQuery, sort scalar_query, cardinality scalar.

Inherited methods

From nu.lang.forms.Form:

Call	Builds	Meaning
`.is_empty()`	`Bool`	True if this Form yields the EMPTY sentinel.
`.is_invalid()`	`Bool`	True if this Form yields the INVALID sentinel.
`.is_sentinel()`	`Bool`	True if this Form yields either sentinel (EMPTY or INVALID).
`.not_empty()`	`Bool`	True if this Form does not yield EMPTY.
`.not_invalid()`	`Bool`	True if this Form does not yield INVALID.

Undocumented: example.