haspara-0.0.0.2: A library providing definitions to work with monetary values.
Safe HaskellNone
LanguageHaskell2010

Haspara.Quantity

Description

This module provides definitions for modeling and working with quantities with fixed decimal points.

Synopsis

Data Definition

 

newtype Quantity (s :: Nat) Source #

Type encoding for quantity values with a given scaling (digits after the decimal point).

>>> 42 :: Quantity 0
42
>>> 42 :: Quantity 1
42.0
>>> 42 :: Quantity 2
42.00
>>> 41 + 1 :: Quantity 2
42.00
>>> 43 - 1 :: Quantity 2
42.00
>>> 2 * 3 * 7 :: Quantity 2
42.00
>>> negate (-42) :: Quantity 2
42.00
>>> abs (-42) :: Quantity 2
42.00
>>> signum (-42) :: Quantity 2
-1.00
>>> fromInteger 42 :: Quantity 2
42.00
>>> mkQuantity 0.415 :: Quantity 2
0.42
>>> mkQuantity 0.425 :: Quantity 2
0.42
>>> mkQuantityLossless 0.42 :: Either String (Quantity 2)
Right 0.42
>>> mkQuantityLossless 0.415 :: Either String (Quantity 2)
Left "Underflow while trying to create quantity: 0.415"

Instances

Instances details
Lift (Quantity s :: Type) Source #

Lift instance for Quantity.

Instance details

Defined in Haspara.Quantity

Methods

lift :: Quantity s -> Q Exp #

liftTyped :: Quantity s -> Q (TExp (Quantity s)) #

Eq (Quantity s) Source # 
Instance details

Defined in Haspara.Quantity

Methods

(==) :: Quantity s -> Quantity s -> Bool #

(/=) :: Quantity s -> Quantity s -> Bool #

KnownNat s => Fractional (Arith (Quantity s)) Source #

Fractional arithmetic over Quantity values.

>>> import Numeric.Decimal
>>> arithM (fromRational 0.42) :: Either SomeException (Quantity 2)
Right 0.42
>>> arithM (fromRational 0.415) :: Either SomeException (Quantity 2)
Left PrecisionLoss (83 % 200) to 2 decimal spaces
>>> arithM $ (fromRational 0.84) / (fromRational 2) :: Either SomeException (Quantity 2)
Right 0.42
>>> arithM $ (fromRational 0.42) / (fromRational 0) :: Either SomeException (Quantity 2)
Left divide by zero
>>> let a = 84 :: Quantity 2
>>> let b =  2 :: Quantity 2
>>> let c =  0 :: Quantity 2
>>> arithM (Arith a / Arith b) :: Either SomeException (Quantity 2)
Right 42.00
>>> arithM (Arith a / Arith b / Arith c) :: Either SomeException (Quantity 2)
Left divide by zero
Instance details

Defined in Haspara.Quantity

KnownNat s => Num (Arith (Quantity s)) Source #

Numeric arithmetic over Quantity values.

>>> import Numeric.Decimal
>>> let a = Arith (mkQuantity 10) + Arith (mkQuantity 32) :: Arith (Quantity 2)
>>> arithMaybe a
Just 42.00
>>> arithM (41 + 1) :: Either SomeException (Quantity 2)
Right 42.00
>>> arithM (43 - 1) :: Either SomeException (Quantity 2)
Right 42.00
>>> arithM (2 * 3 * 7) :: Either SomeException (Quantity 2)
Right 42.00
>>> arithM (signum 42) :: Either SomeException (Quantity 2)
Right 1.00
>>> arithM (signum (-42)) :: Either SomeException (Quantity 2)
Right -1.00
>>> arithM (abs 42) :: Either SomeException (Quantity 2)
Right 42.00
>>> arithM (abs (-42)) :: Either SomeException (Quantity 2)
Right 42.00
>>> arithM (fromInteger 42) :: Either SomeException (Quantity 2)
Right 42.00
Instance details

Defined in Haspara.Quantity

KnownNat s => Num (Quantity s) Source # 
Instance details

Defined in Haspara.Quantity

Ord (Quantity s) Source # 
Instance details

Defined in Haspara.Quantity

Methods

compare :: Quantity s -> Quantity s -> Ordering #

(<) :: Quantity s -> Quantity s -> Bool #

(<=) :: Quantity s -> Quantity s -> Bool #

(>) :: Quantity s -> Quantity s -> Bool #

(>=) :: Quantity s -> Quantity s -> Bool #

max :: Quantity s -> Quantity s -> Quantity s #

min :: Quantity s -> Quantity s -> Quantity s #

KnownNat s => Show (Quantity s) Source #

Show instance for Quantity.

>>> show (42 :: Quantity 2)
"42.00"
>>> 42 :: Quantity 2
42.00
Instance details

Defined in Haspara.Quantity

Methods

showsPrec :: Int -> Quantity s -> ShowS #

show :: Quantity s -> String #

showList :: [Quantity s] -> ShowS #

Generic (Quantity s) Source # 
Instance details

Defined in Haspara.Quantity

Associated Types

type Rep (Quantity s) :: Type -> Type #

Methods

from :: Quantity s -> Rep (Quantity s) x #

to :: Rep (Quantity s) x -> Quantity s #

KnownNat s => ToJSON (Quantity s) Source #

ToJSON instance for Quantity.

>>> Aeson.encode (mkQuantity 0.42 :: Quantity 2)
"0.42"
Instance details

Defined in Haspara.Quantity

KnownNat s => FromJSON (Quantity s) Source #

FromJSON instance for Quantity.

>>> Aeson.decode "0.42" :: Maybe (Quantity 2)
Just 0.42
>>> Aeson.decode "0.415" :: Maybe (Quantity 2)
Just 0.42
>>> Aeson.decode "0.425" :: Maybe (Quantity 2)
Just 0.42
Instance details

Defined in Haspara.Quantity

type Rep (Quantity s) Source # 
Instance details

Defined in Haspara.Quantity

type Rep (Quantity s) = D1 ('MetaData "Quantity" "Haspara.Quantity" "haspara-0.0.0.2-AxwfIaY3JAe5J0iuX9jCcl" 'True) (C1 ('MetaCons "MkQuantity" 'PrefixI 'True) (S1 ('MetaSel ('Just "unQuantity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (Decimal RoundHalfEven s Integer))))

type UnsignedQuantity s = Refined NonNegative (Quantity s) Source #

Type definition for unsigned Quantity values.

Smart Constructors

 

mkQuantity :: KnownNat s => Scientific -> Quantity s Source #

Constructs Quantity values from Scientific values in a lossy way.

This function uses mkQuantityAux in case that the lossless attempt fails. We could have used mkQuantityAux directly. However, mkQuantityAux is doing too much (see roundScientific). Therefore, we are first attempting a lossless construction (see mkQuantityLossless) and we fallback to mkQuantityAux in case the lossless construction fails.

>>> mkQuantity 0 :: Quantity 0
0
>>> mkQuantity 0 :: Quantity 1
0.0
>>> mkQuantity 0 :: Quantity 2
0.00
>>> mkQuantity 0.04 :: Quantity 1
0.0
>>> mkQuantity 0.05 :: Quantity 1
0.0
>>> mkQuantity 0.06 :: Quantity 1
0.1
>>> mkQuantity 0.14 :: Quantity 1
0.1
>>> mkQuantity 0.15 :: Quantity 1
0.2
>>> mkQuantity 0.16 :: Quantity 1
0.2
>>> mkQuantity 0.04 :: Quantity 2
0.04
>>> mkQuantity 0.05 :: Quantity 2
0.05
>>> mkQuantity 0.06 :: Quantity 2
0.06
>>> mkQuantity 0.14 :: Quantity 2
0.14
>>> mkQuantity 0.15 :: Quantity 2
0.15
>>> mkQuantity 0.16 :: Quantity 2
0.16
>>> mkQuantity 0.04 :: Quantity 3
0.040
>>> mkQuantity 0.05 :: Quantity 3
0.050
>>> mkQuantity 0.06 :: Quantity 3
0.060
>>> mkQuantity 0.14 :: Quantity 3
0.140
>>> mkQuantity 0.15 :: Quantity 3
0.150
>>> mkQuantity 0.16 :: Quantity 3
0.160

mkQuantityLossless :: (KnownNat s, MonadError String m) => Scientific -> m (Quantity s) Source #

Constructs Quantity values from Scientific values in a lossy way.

>>> mkQuantityLossless 0 :: Either String (Quantity 0)
Right 0
>>> mkQuantityLossless 0 :: Either String (Quantity 1)
Right 0.0
>>> mkQuantityLossless 0 :: Either String (Quantity 2)
Right 0.00
>>> mkQuantityLossless 0.04 :: Either String (Quantity 1)
Left "Underflow while trying to create quantity: 4.0e-2"
>>> mkQuantityLossless 0.05 :: Either String (Quantity 1)
Left "Underflow while trying to create quantity: 5.0e-2"
>>> mkQuantityLossless 0.06 :: Either String (Quantity 1)
Left "Underflow while trying to create quantity: 6.0e-2"
>>> mkQuantityLossless 0.14 :: Either String (Quantity 1)
Left "Underflow while trying to create quantity: 0.14"
>>> mkQuantityLossless 0.15 :: Either String (Quantity 1)
Left "Underflow while trying to create quantity: 0.15"
>>> mkQuantityLossless 0.16 :: Either String (Quantity 1)
Left "Underflow while trying to create quantity: 0.16"
>>> mkQuantityLossless 0.04 :: Either String (Quantity 2)
Right 0.04
>>> mkQuantityLossless 0.05 :: Either String (Quantity 2)
Right 0.05
>>> mkQuantityLossless 0.06 :: Either String (Quantity 2)
Right 0.06
>>> mkQuantityLossless 0.14 :: Either String (Quantity 2)
Right 0.14
>>> mkQuantityLossless 0.15 :: Either String (Quantity 2)
Right 0.15
>>> mkQuantityLossless 0.16 :: Either String (Quantity 2)
Right 0.16
>>> mkQuantityLossless 0.04 :: Either String (Quantity 3)
Right 0.040
>>> mkQuantityLossless 0.05 :: Either String (Quantity 3)
Right 0.050
>>> mkQuantityLossless 0.06 :: Either String (Quantity 3)
Right 0.060
>>> mkQuantityLossless 0.14 :: Either String (Quantity 3)
Right 0.140
>>> mkQuantityLossless 0.15 :: Either String (Quantity 3)
Right 0.150
>>> mkQuantityLossless 0.16 :: Either String (Quantity 3)
Right 0.160

Utilities

 

roundQuantity :: KnownNat k => Quantity (n + k) -> Quantity n Source #

Rounds given quantity by k digits.

>>> roundQuantity (mkQuantity 0.415 :: Quantity 3) :: Quantity 2
0.42
>>> roundQuantity (mkQuantity 0.425 :: Quantity 3) :: Quantity 2
0.42

times :: (KnownNat s, KnownNat k) => Quantity s -> Quantity k -> Quantity s Source #

Multiplies two quantities with different scales and rounds back to the scale of the frst operand.

>>> times (mkQuantity 0.42 :: Quantity 2) (mkQuantity 0.42 :: Quantity 2)
0.18

timesLossless :: (KnownNat s, KnownNat k) => Quantity s -> Quantity k -> Quantity (s + k) Source #

Multiplies two quantities with different scales.

>>> timesLossless (mkQuantity 0.42 :: Quantity 2) (mkQuantity 0.42 :: Quantity 2)
0.1764

Internal

 

mkQuantityAux :: forall s. KnownNat s => Scientific -> Quantity s Source #

Auxiliary function for constructing Quantity values.

See mkQuantity why we need this function and why we haven't used it as the direct implementation of mkQuantity.

Call-sites should avoid using this function directly due to its performance characteristics.

roundScientific :: Int -> Scientific -> Scientific Source #

Rounds a given scientific into a new scientific with given max digits after decimal point.

This uses half-even rounding method.

>>> roundScientific 0 0.4
0.0
>>> roundScientific 0 0.5
0.0
>>> roundScientific 0 0.6
1.0
>>> roundScientific 0 1.4
1.0
>>> roundScientific 0 1.5
2.0
>>> roundScientific 0 1.6
2.0
>>> roundScientific 1 0.04
0.0
>>> roundScientific 1 0.05
0.0
>>> roundScientific 1 0.06
0.1
>>> roundScientific 1 0.14
0.1
>>> roundScientific 1 0.15
0.2
>>> roundScientific 1 0.16
0.2
>>> roundScientific 1 3.650
3.6
>>> roundScientific 1 3.740
3.7
>>> roundScientific 1 3.749
3.7
>>> roundScientific 1 3.750
3.8
>>> roundScientific 1 3.751
3.8
>>> roundScientific 1  3.760
3.8
>>> roundScientific 1 (-3.650)
-3.6
>>> roundScientific 1 (-3.740)
-3.7
>>> roundScientific 1 (-3.749)
-3.7
>>> roundScientific 1 (-3.750)
-3.8
>>> roundScientific 1 (-3.751)
-3.8
>>> roundScientific 1 (-3.760)
-3.8

TODO: Refactor to improve the performance of this function.

Orphan instances

Lift (Decimal RoundHalfEven s Integer :: Type) Source #

Orphan Lift instance for Quantity.

TODO: Avoid having an orphan instance for Decimal r s p?

Instance details