Haspara.Quantity

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

Data Definition

newtype Quantity (s :: Nat)

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"

Constructors

MkQuantity

Fields

• unQuantity :: Decimal RoundHalfEven s Integer

Instances

Lift (Quantity s :: Type)

Lift instance for Quantity.

Defined in Haspara.Quantity

Methods

lift :: Quantity s -> Q Exp

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

Eq (Quantity s)

Defined in Haspara.Quantity

Methods

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

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

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

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

Defined in Haspara.Quantity

Methods

(/) :: Arith (Quantity s) -> Arith (Quantity s) -> Arith (Quantity s)

recip :: Arith (Quantity s) -> Arith (Quantity s)

fromRational :: Rational -> Arith (Quantity s)

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

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

Defined in Haspara.Quantity

Methods

(+) :: Arith (Quantity s) -> Arith (Quantity s) -> Arith (Quantity s)

(-) :: Arith (Quantity s) -> Arith (Quantity s) -> Arith (Quantity s)

(*) :: Arith (Quantity s) -> Arith (Quantity s) -> Arith (Quantity s)

negate :: Arith (Quantity s) -> Arith (Quantity s)

abs :: Arith (Quantity s) -> Arith (Quantity s)

signum :: Arith (Quantity s) -> Arith (Quantity s)

fromInteger :: Integer -> Arith (Quantity s)

KnownNat s => Num (Quantity s)

Defined in Haspara.Quantity

Methods

(+) :: Quantity s -> Quantity s -> Quantity s

(-) :: Quantity s -> Quantity s -> Quantity s

(*) :: Quantity s -> Quantity s -> Quantity s

negate :: Quantity s -> Quantity s

abs :: Quantity s -> Quantity s

signum :: Quantity s -> Quantity s

fromInteger :: Integer -> Quantity s

Ord (Quantity s)

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)

Show instance for Quantity.

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

Defined in Haspara.Quantity

Methods

showsPrec :: Int -> Quantity s -> ShowS

show :: Quantity s -> String

showList :: [Quantity s] -> ShowS

Generic (Quantity s)

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)

ToJSON instance for Quantity.

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

Defined in Haspara.Quantity

Methods

toJSON :: Quantity s -> Value

toEncoding :: Quantity s -> Encoding

toJSONList :: [Quantity s] -> Value

toEncodingList :: [Quantity s] -> Encoding

KnownNat s => FromJSON (Quantity s)

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

Defined in Haspara.Quantity

Methods

parseJSON :: Value -> Parser (Quantity s)

parseJSONList :: Value -> Parser [Quantity s]

type Rep (Quantity s)

Defined in Haspara.Quantity

type Rep (Quantity s) = D1 ('MetaData "Quantity" "Haspara.Quantity" "haspara-0.0.0.4-91kyQ1gsJrx6JOOKY5ajCi" '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)

Type definition for unsigned Quantity values.

Smart Constructors

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

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)

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

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

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)

Multiplies two quantities with different scales.

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

sumUnsignedQuantity :: KnownNat s => [UnsignedQuantity s] -> UnsignedQuantity s

Returns the total of a list of unsigned quantities.

>>> sumUnsignedQuantity [] :: UnsignedQuantity 2
Refined 0.00

absQuantity :: KnownNat s => Quantity s -> UnsignedQuantity s

Returns the absolute value of the Quantity as UnsignedQuantity.

>>> abs (mkQuantity 0.42 :: Quantity 2)
0.42
>>> abs (mkQuantity 0 :: Quantity 2)
0.00
>>> abs (mkQuantity (-0.42) :: Quantity 2)
0.42

Internal

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

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

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)

Orphan Lift instance for Quantity.

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

Methods

lift :: Decimal RoundHalfEven s Integer -> Q Exp

liftTyped :: Decimal RoundHalfEven s Integer -> Q (TExp (Decimal RoundHalfEven s Integer))