Module Roman

Library for roman numbers. This library defines a datatype Roman to represent roman numbers, conversion operations fromInt and toInt to convert integers into roman numbers and back, and an operation showRoman to show roman numbers as strings.

Author: Bernd Brassel, Michael Hanus

Version: 0.0.1

Summary of exported operations:

regular
                  :: Roman -> Bool

Is a given roman number well formed?

showRoman
                  :: Roman -> String

Shows roman numbers in the usual way.

showsRoman
                  :: Roman -> String -> String

Shows roman numbers continuation style.

toInt
                  :: Roman -> Int

Converts a roman number to an integer.

fromInt
                  :: Int -> Roman

Converts integers to roman numbers.

Exported datatypes:

Roman

The type to represent roman numbers. Examples:

"IV"   =  Minus I V
"III"  =  Plus I (Plus I I)

Constructors:

I :: Roman
V :: Roman
X :: Roman
L :: Roman
C :: Roman
D :: Roman
M :: Roman
Minus :: Roman -> Roman -> Roman
Plus :: Roman -> Roman -> Roman

Exported operations:

regular :: Roman -> Bool

Is a given roman number well formed?

showRoman :: Roman -> String

Shows roman numbers in the usual way.

showsRoman :: Roman -> String -> String

Shows roman numbers continuation style.

toInt :: Roman -> Int

Converts a roman number to an integer.

fromInt :: Int -> Roman

Converts integers to roman numbers. Since we have no over/underlining, we can only represent positive integers which are smaller than 4000.