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Version: 3.0.1

Humanizer.RomanNumeralExtensions

RomanNumeralExtensions Class​

Contains extension methods for changing a number to Roman representation (ToRoman) and from Roman representation back to the number (FromRoman)

public static class RomanNumeralExtensions

Inheritance System.Object → RomanNumeralExtensions

Methods​

RomanNumeralExtensions.FromRoman(ReadOnlySpan<char>) Method​

Converts a Roman numeral character span to its integer representation.

public static int FromRoman(System.ReadOnlySpan<char> input);

Parameters​

input System.ReadOnlySpan<System.Char>

The Roman numeral character span to convert. Must not be empty.

Returns​

System.Int32
The integer value represented by the Roman numeral.

Exceptions​

System.ArgumentException
Thrown when input is empty (after trimming) or contains an invalid Roman numeral format.

Example​

"XIV".AsSpan().FromRoman() => 14
"MCMXC".AsSpan().FromRoman() => 1990

Remarks​

This is a memory-efficient overload that works with character spans to avoid string allocations. Valid Roman numerals use the characters M, D, C, L, X, V, and I (case-insensitive). Supports subtractive notation (e.g., IV = 4, IX = 9).

RomanNumeralExtensions.FromRoman(this string) Method​

Converts a Roman numeral string to its integer representation.

public static int FromRoman(this string input);

Parameters​

input System.String

The Roman numeral string to convert (e.g., "XIV", "MCMXC"). Must not be null.

Returns​

System.Int32
The integer value represented by the Roman numeral.

Exceptions​

System.ArgumentNullException
Thrown when input is null.

System.ArgumentException
Thrown when input is empty or contains an invalid Roman numeral format.

Example​

"XIV".FromRoman() => 14
"MCMXC".FromRoman() => 1990
"IV".FromRoman() => 4
"MMXXIII".FromRoman() => 2023

Remarks​

Valid Roman numerals use the characters M, D, C, L, X, V, and I (case-insensitive). Supports subtractive notation (e.g., IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900). Valid range is 1 to 3999.

RomanNumeralExtensions.ToRoman(this int) Method​

Converts an integer to its Roman numeral representation.

public static string ToRoman(this int input);

Parameters​

input System.Int32

The integer value to convert. Must be between 1 and 3999 inclusive.

Returns​

System.String
A string containing the Roman numeral representation of the input value.

Exceptions​

System.ArgumentOutOfRangeException
Thrown when input is less than 1 or greater than 3999. Roman numerals are traditionally limited to this range.

Example​

14.ToRoman() => "XIV"
1990.ToRoman() => "MCMXC"
4.ToRoman() => "IV"
2023.ToRoman() => "MMXXIII"
3999.ToRoman() => "MMMCMXCIX"

Remarks​

Uses standard Roman numeral notation including subtractive notation for 4, 9, 40, 90, 400, and 900. The implementation is optimized for performance and avoids string allocations where possible.