Fcf.Utils

Type-level error.

TypeError as a fcf.

Conjunction of a list of constraints.

Type equality.

Details

The base library also defines a similar (Type.Equality.==); it differs from TyEq in the following ways:

• TyEq is heterogeneous: its arguments may have different kinds;

• TyEq is reflexive: TyEq a a always reduces to True even if a is a variable.

A stuck type that can be used like a type-level undefined.

(Limited) equivalent of \case { .. } syntax. Supports matching of exact values (-->) and final matches for any value (Any) or for passing value to subcomputation (Else). Examples:

type BoolToNat = Case
  [ 'True  --> 0
  , 'False --> 1
  ]

type NatToBool = Case
  [ 0 --> 'False
  , Any   'True
  ]

type ZeroOneOrSucc = Case
  [ 0  --> 0
  , 1  --> 1
  , Else   ((+) 1)
  ]

Match concrete type in Case.

Match on predicate being successful with type in Case.

Match any type in Case. Should be used as a final branch.

Note: this identifier conflicts with Any (from Fcf.Class.Foldable) Any (from Data.Monoid), and Any (from GHC.Exts).

We recommend importing this one qualified.

Pass type being matched in Case to subcomputation. Should be used as a final branch.

Type-level If. If True a b ==> a; If False a b ==> b