| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell98 |
Text.Numeral.Roman
Description
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.
Example:
> toRoman 1729 ∷ String
"MDCCXXIX"
> fromRoman "MDCCXXIX" ∷ Maybe Integer
Just 1729
>convertTosimpleRoman1729 ∷ String "MDCCXXVIIII"
> fromRoman "Bla" ∷ Maybe Integer
Nothing
- 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
- spNull :: s -> Bool
- spStripPrefix :: s -> s -> Maybe s
- convertFrom :: (Monoid s, StripPrefix s, Eq s, Ord n, Num n) => NumeralConfig s n -> s -> Maybe 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) => s -> Maybe n
Types
data NumeralConfig s n Source
A configuration with which the convertTo and convertFrom functions can
be parameterized.
Arguments
| :: (Ord n, Num n) | |
| => s | Symbol for zero |
| -> s | Symbol for one |
| -> [(s, n)] | Symbol-value table. |
| -> NumeralConfig s n |
Smart constructor for a NumeralConfig.
Pretty printing
convertTo :: Monoid s => Ord n => Num n => NumeralConfig s n -> n -> s Source
Converts a number to a Roman numeral according to the given configuration.
Parsing
convertFrom :: (Monoid s, StripPrefix s, Eq s, Ord n, Num n) => NumeralConfig s n -> s -> Maybe n Source
Parses a string as a Roman numeral according to the given
configuration. Result is Nothing if the input is not a valid numeral.
Default Configurations
modernRoman :: (IsString s, Ord n, Num n) => NumeralConfig s n Source
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 an empty string. Larger numbers will result in repeated use of the 'M' symbol.
simpleRoman :: (IsString s, Ord n, Num n) => NumeralConfig s n Source
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]. Smaller numbers will result in an empty string. Larger numbers will result in repeated use of the 'M' symbol.