Parsing and pretty printing of Roman numerals.
This module provides functions for parsing and pretty printing Roman numerals. Because the notation of Roman numerals has varied through the centuries this package allows for some customisation using a configuration that is passed to the conversion functions. Exceptions are dealt with by wrapping the results of conversions in the error monad.
toRoman1729 ∷ String "MDCCXXIX"
fromRoman"MDCCXXIX" ∷ Either String Integer Right 1729
simpleRoman1729 ∷ String "MDCCXXVIIII"
fromRoman"Bla" ∷ Either String Integer Left "Roman.convertFrom: can't parse"
- data NumeralConfig s n
- mkNumConfig :: (Ord n, Num n) => s -> s -> [(s, n)] -> NumeralConfig s n
- convertTo :: Monoid s => Ord n => Num n => NumeralConfig s n -> n -> s
- class StripPrefix s where
- convertFrom :: (Monoid s, StripPrefix s, Eq s, Ord n, Num n, MonadError String m) => NumeralConfig s n -> s -> m n
- modernRoman :: (IsString s, Ord n, Num n) => NumeralConfig s n
- simpleRoman :: (IsString s, Ord n, Num n) => NumeralConfig s n
- toRoman :: (IsString s, Monoid s, Ord n, Num n) => n -> s
- fromRoman :: (IsString s, Monoid s, StripPrefix s, Eq s, Ord n, Num n, MonadError String m) => s -> m n
|:: (Ord n, Num n)|
Symbol for zero
Symbol for one
|-> [(s, n)]|
|-> NumeralConfig s n|
Smart constructor for a
Converts a number to a Roman numeral according to the given configuration. Numbers which are out of bounds will cause exceptions to be thrown. An exception will also be raised if no representation is possible with the given configuration. If the value of any symbol in the configuration is equal to 0 or a symbol is the empty string this function is undefined.
Class used to overload the input of the parsing functions.
Parses a string as a Roman numeral according to the given configuration. An exception will be thrown if the input is not a valid numeral.
Configuration for Roman numerals as they are commonly used today. The value 0 is represented by the empty string. It can be interpreted as not writing down a number. This configuration is practically limited to the range [1..3999]. Smaller numbers will result in empty string. Larger numbers will result in repeated use of the 'M' symbol.
Configuration for Roman numerals that do not use the rule that a lower rank symbol can be placed before a higher rank symbol to denote the difference between them. Thus a numeral like "IV" will not be accepted or generated by this configuration. This configuration is practically limited to the range [1..3999]. Larger numbers will result in repeated use of the 'M' symbol.
Converts a number to a modern Roman numeral. See