Provides a type describing the pattern functor of some {co}recursive type
T. For standard fixed-point types like matryoshka.data.Fix,
Based[Fix[F]]#Base is simply F. However, directly recursive types
generally have a less obvious pattern functor. E.g., Based[Cofree[F,
A]]#Base is EnvT[A, F, ?].
Provides a type describing the pattern functor of some {co}recursive type
T. For standard fixed-point types like matryoshka.data.Fix,Based[Fix[F]]#Baseis simplyF. However, directly recursive types generally have a less obvious pattern functor. E.g.,Based[Cofree[F, A]]#BaseisEnvT[A, F, ?].