o-clock has a few functions for converting between Time units, or from Time unit to something else.
In general, we use ExplicitForAll and order the type variables so that the target type comes first and the source type comes last:
toUnit :: forall (unitTo :: Rat) (unitFrom :: Rat). KnownDivRat unitFrom unitTo => Time unitFrom -> Time unitTo
toNum :: forall (unitTo :: Rat) n (unit :: Rat). (KnownDivRat unit unitTo, Num n) => Time unit -> n
We do this under the assumption that the type of the argument is usually explicit or can be inferred by GHC, so the user will almost always be more interested in specifying the target type using TypeApplications (and omit the source type):
-- We can omit the source type @Hour
λ> toUnit @Minute $ hour 3
180m
-- We can omit the source type @Hour
λ> toNum @Minute @Int $ hour 3
180
However, floorRat seems to be the odd one out:
floorRat :: forall (unit :: Rat) b. Integral b => Time unit -> b
λ> floorRat @_ @Int $ hour 3
3
For consistency, we should reorder the type variables of floorRat.
o-clockhas a few functions for converting betweenTime units, or fromTime unitto something else.In general, we use
ExplicitForAlland order the type variables so that the target type comes first and the source type comes last:We do this under the assumption that the type of the argument is usually explicit or can be inferred by GHC, so the user will almost always be more interested in specifying the target type using TypeApplications (and omit the source type):
However,
floorRatseems to be the odd one out:For consistency, we should reorder the type variables of
floorRat.