Is
Related Docs:
object Is
| package evidence
To create an instance of A Is B you must show that for every choice
of F[_] you can convert F[A] to F[B].
To create an instance of A Is B you must show that for every choice
of F[_] you can convert F[A] to F[B]. Loosely, this reads as
saying that B must have the same effect as A in all contexts
therefore allowing type substitution.
Is is transitive and therefore values of Is can be composed in a
chain much like functions.
Is is transitive and therefore values of Is can be composed in a
chain much like functions. See also compose.
Substitution on identity brings about a direct coercion function of the
same form that =:= provides.
Substitution on identity brings about a direct coercion function of the
same form that =:= provides.
Is is transitive and therefore values of Is can be composed in a
chain much like functions.
Is is transitive and therefore values of Is can be composed in a
chain much like functions. See also andThen.
Is is symmetric and therefore can be flipped around.
Is is symmetric and therefore can be flipped around. Flipping is its
own inverse, so x.flip.flip == x.
Sometimes for more complex substitutions it helps the typechecker to
wrap one layer of F[_] context around the types you're equating
before substitution.
Sometimes for more complex substitutions it helps the typechecker to
wrap one layer of F[_] context around the types you're equating
before substitution.
A value A Is B is always sufficient to produce a similar Predef.=:=
value.
A value A Is B is always sufficient to produce a similar Predef.=:=
value.
A value of
A Is Bis proof that the typesAandBare the same. More powerfully, it asserts that they have the same meaning in all type contexts. This can be a more powerful assertion thanA =:= Band is more easily used in manipulation of types while avoiding (potentially erroneous) coercions.A Is Bis also known as Leibniz equality.