Type encoding for currency symbol values with a syntax of [A-Z]{3}[A-Z]*.

Currency values can be constructed via mkCurrencyError that works in MonadError Text context:

>>> :set -XOverloadedStrings
>>> mkCurrencyError "EUR" :: Either T.Text Currency
Right EUR

... or via mkCurrencyFail that works in MonadFail context:

>>> mkCurrencyFail "EUR" :: Maybe Currency
Just EUR

An IsString instance is provided as well which is unsafe but convenient:

>>> "EUR" :: Currency
EUR

Smart constructor for Currency values within MonadError context.

>>> :set -XOverloadedStrings
>>> mkCurrencyError "" :: Either T.Text Currency
Left "Currency code error! Expecting at least 3 uppercase ASCII letters, but received: "
>>> mkCurrencyError " " :: Either T.Text Currency
Left "Currency code error! Expecting at least 3 uppercase ASCII letters, but received:  "
>>> mkCurrencyError "AB" :: Either T.Text Currency
Left "Currency code error! Expecting at least 3 uppercase ASCII letters, but received: AB"
>>> mkCurrencyError " ABC " :: Either T.Text Currency
Left "Currency code error! Expecting at least 3 uppercase ASCII letters, but received:  ABC "
>>> mkCurrencyError "ABC" :: Either T.Text Currency
Right ABC

Smart constructor for Currency values within MonadFail context.

>>> :set -XOverloadedStrings
>>> mkCurrencyFail "" :: Maybe Currency
Nothing
>>> mkCurrencyFail "US" :: Maybe Currency
Nothing
>>> mkCurrencyFail "usd" :: Maybe Currency
Nothing
>>> mkCurrencyFail "USD" :: Maybe Currency
Just USD

Parser that parses currency codes.

>>> :set -XOverloadedStrings
>>> MP.runParser currencyCodeParser "Example" ""
Left (ParseErrorBundle {bundleErrors = TrivialError 0 (Just EndOfInput) (fromList []) :| [], bundlePosState = PosState {pstateInput = "", pstateOffset = 0, pstateSourcePos = SourcePos {sourceName = "Example", sourceLine = Pos 1, sourceColumn = Pos 1}, pstateTabWidth = Pos 8, pstateLinePrefix = ""}})
>>> MP.runParser currencyCodeParser "Example" " "
Left (ParseErrorBundle {bundleErrors = TrivialError 0 (Just (Tokens (' ' :| ""))) (fromList []) :| [], bundlePosState = PosState {pstateInput = " ", pstateOffset = 0, pstateSourcePos = SourcePos {sourceName = "Example", sourceLine = Pos 1, sourceColumn = Pos 1}, pstateTabWidth = Pos 8, pstateLinePrefix = ""}})
>>> MP.runParser currencyCodeParser "Example" "a"
Left (ParseErrorBundle {bundleErrors = TrivialError 0 (Just (Tokens ('a' :| ""))) (fromList []) :| [], bundlePosState = PosState {pstateInput = "a", pstateOffset = 0, pstateSourcePos = SourcePos {sourceName = "Example", sourceLine = Pos 1, sourceColumn = Pos 1}, pstateTabWidth = Pos 8, pstateLinePrefix = ""}})
>>> MP.runParser currencyCodeParser "Example" "A"
Left (ParseErrorBundle {bundleErrors = TrivialError 1 (Just EndOfInput) (fromList []) :| [], bundlePosState = PosState {pstateInput = "A", pstateOffset = 0, pstateSourcePos = SourcePos {sourceName = "Example", sourceLine = Pos 1, sourceColumn = Pos 1}, pstateTabWidth = Pos 8, pstateLinePrefix = ""}})
>>> MP.runParser currencyCodeParser "Example" "AB"
Left (ParseErrorBundle {bundleErrors = TrivialError 2 (Just EndOfInput) (fromList []) :| [], bundlePosState = PosState {pstateInput = "AB", pstateOffset = 0, pstateSourcePos = SourcePos {sourceName = "Example", sourceLine = Pos 1, sourceColumn = Pos 1}, pstateTabWidth = Pos 8, pstateLinePrefix = ""}})
>>> MP.runParser currencyCodeParser "Example" "ABC"
Right "ABC"
>>> MP.runParser currencyCodeParser "Example" "ABCD"
Right "ABCD"
>>> MP.runParser currencyCodeParser "Example" " ABCD "
Left (ParseErrorBundle {bundleErrors = TrivialError 0 (Just (Tokens (' ' :| ""))) (fromList []) :| [], bundlePosState = PosState {pstateInput = " ABCD ", pstateOffset = 0, pstateSourcePos = SourcePos {sourceName = "Example", sourceLine = Pos 1, sourceColumn = Pos 1}, pstateTabWidth = Pos 8, pstateLinePrefix = ""}})

Type encoding of a currency pair.

CurrencyPair values are constructed via the data constructor:

>>> :set -XOverloadedStrings
>>> CurrencyPair "EUR" "USD"
EUR/USD

FromJSON and ToJSON instances are provided as well:

>>> Aeson.decode "{\"base\": \"EUR\", \"quote\": \"EUR\"}" :: Maybe CurrencyPair
Just EUR/EUR
>>> Aeson.encode (CurrencyPair "EUR" "USD")
"{\"base\":\"EUR\",\"quote\":\"USD\"}"

Converts a CurrencyPair to a 2-tuple of Currency values.

>>> :set -XOverloadedStrings
>>> toCurrencyTuple (CurrencyPair "EUR" "USD")
(EUR,USD)

Converts a 2-tuple of Currency values to a CurrencyPair.

>>> :set -XOverloadedStrings
>>> fromCurrencyTuple ("EUR", "USD")
EUR/USD