| Copyright | Copyright (C) 2006-2018 Bjorn Buckwalter |
|---|---|
| License | BSD3 |
| Maintainer | bjorn@buckwalter.se |
| Stability | Experimental |
| Portability | GHC only? |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Numeric.Units.Dimensional.Coercion
Description
Re-exports the raw Quantity constructor from the Numeric.Units.Dimensional.Internal module, along with coerce,
for convenience in converting between raw representations and dimensional values.
Note that use of these constructs requires the user to verify the dimensional safety of the conversion,
because the coercion doesn't explicitly mention the unit of the representation. Note also that the
Quantity constructor constructs a SQuantity which may have a scale factor
other than One.
Note that the haddock documentation doesn't mention the Quantity constructor because it is a part of the
Dimensional associated data family, but it is exported by this module.
Synopsis
- coerce :: forall {k :: RuntimeRep} (a :: TYPE k) (b :: TYPE k). Coercible a b => a -> b
- data family Dimensional v :: Dimension -> Type -> Type
- unQuantity :: SQuantity s d a -> a
Documentation
coerce :: forall {k :: RuntimeRep} (a :: TYPE k) (b :: TYPE k). Coercible a b => a -> b Source #
The function coerce allows you to safely convert between values of
types that have the same representation with no run-time overhead. In the
simplest case you can use it instead of a newtype constructor, to go from
the newtype's concrete type to the abstract type. But it also works in
more complicated settings, e.g. converting a list of newtypes to a list of
concrete types.
When used in conversions involving a newtype wrapper, make sure the newtype constructor is in scope.
This function is representation-polymorphic, but the
RuntimeRep type argument is marked as Inferred, meaning
that it is not available for visible type application. This means
the typechecker will accept coerce @Int @Age 42
Examples
>>>newtype TTL = TTL Int deriving (Eq, Ord, Show)>>>newtype Age = Age Int deriving (Eq, Ord, Show)>>>coerce (Age 42) :: TTLTTL 42>>>coerce (+ (1 :: Int)) (Age 42) :: TTLTTL 43>>>coerce (map (+ (1 :: Int))) [Age 42, Age 24] :: [TTL][TTL 43,TTL 25]
data family Dimensional v :: Dimension -> Type -> Type Source #
A dimensional value, either a Quantity or a Unit, parameterized by its Dimension and representation.