primitives.sentinel

Module nu.forms.primitives.sentinel_.

Sentinel interfaces - SentinelForm, EmptyForm.

Wraps EMPTY so it can appear as a typed Form node in a Nu tree, mainly so is_empty() has something typed to call on.

Name	Sort	Call	Meaning
EmptyForm	`scalar_query`	`EmptyForm()`	Wraps EMPTY, the no-value sentinel.
SentinelForm	`scalar_query`	`SentinelForm()`	Base for the sentinel interfaces.

EmptyForm

Wraps EMPTY, the no-value 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
`a == b`	`Bool`	Self equal to other by value: an `Eq` term, never a Python bool.
`a != b`	`Bool`	Self not equal to other by value: a `Ne` term, never a Python bool.
`.is_empty()`	`Bool`	True if this Form yields the EMPTY sentinel.
`.not_empty()`	`Bool`	True if this Form does not yield EMPTY.
`.fallback(*alternatives)`	`Self`	The first of this value and `alternatives` that is not EMPTY.

Base for the sentinel interfaces.

SentinelForm()

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

Inherited methods

From nu.lang.forms.Form:

Call	Builds	Meaning
`a == b`	`Bool`	Self equal to other by value: an `Eq` term, never a Python bool.
`a != b`	`Bool`	Self not equal to other by value: a `Ne` term, never a Python bool.
`.is_empty()`	`Bool`	True if this Form yields the EMPTY sentinel.
`.not_empty()`	`Bool`	True if this Form does not yield EMPTY.
`.fallback(*alternatives)`	`Self`	The first of this value and `alternatives` that is not EMPTY.

Undocumented: example.