`not`

Boolean negation as a function you can pass around.

bool not(bool a) => !a;

Lecture

not does exactly what !a does — it just does it as a first-class function, so it can be passed where a bool Function(bool) is expected instead of you writing (b) => !b yourself. FxTS's not works on JavaScript "truthy" values of any type; Dart has no implicit truthiness, so the Dart port only accepts an actual bool.

Because its signature is bool -> bool, not doubles as a predicate itself wherever the element type is already bool — see some/every in Demo 2. For negating an arbitrary predicate over some other type, use negate instead.

Demo 1 · Basics

Demo 2 · As a predicate over booleans

not is itself a bool Function(bool), so it plugs straight into some/every without wrapping:

Try it yourself

Exercise: use not to build the list of "still pending" flags from a list of "done" flags.

Related: negate — negate a whole predicate function, not just a bool · some / every — used with not above · when — conditional transform · unless — the inverse-condition sibling of when