Roman Numeral in Lua

Published on 28 April 2022 (Updated: 25 September 2022)

Roman Numeral in Lua

Welcome to the Roman Numeral in Lua page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

#!/bin/lua

-- Key value pairs for roman numerals
conversion_table = {
    ['I']=1,
    ['V']=5,
    ['X']=10,
    ['L']=50,
    ['C']=100,
    ['D']=500,
    ['M']=1000
}

-- Check if character is valid (in conversion table)
function validateCharacter(char) 
    for key,value in pairs(conversion_table) do
        if char == key then
            return true
        end
    end
    return false
end

-- Convert roman numeral to decimal
function convertToDecimal(roman)
    -- If numeral is a single character, simply return value
    if #roman == 1 then
        return conversion_table[roman]
    end

    sum = 0

    -- Iterate through entire number
    for i = 1, #roman do
        current = conversion_table[string.sub(roman, i, i)]
        next = conversion_table[string.sub(roman, i+1, i+1)]
        
        -- Subtract values if first character is smaller, then skip next character
        if (next ~= nil) and (current < next) then
            sum = sum + (next - current)
            break
        -- Add character value to sum
        else
            sum = sum + current
        end
    end

    return sum
end

-- Get input from command line
input = arg[1]

-- Exit if no input given
if arg[1] == nil then
    print('Usage: please provide a string of roman numerals')
    return
end

-- Check each character for validity, exit if any are invalid
for i = 1, #input do
    if validateCharacter(string.sub(input, i, i)) == false then
        print('Error: invalid string of roman numerals')
        return
    end
end

-- Print converted value
print(convertToDecimal(input))

Roman Numeral in Lua was written by:

If you see anything you'd like to change or update, please consider contributing.

Note: The solution shown above is the current solution in the Sample Programs repository as of Oct 15 2020 19:22:39. The solution was first committed on Oct 28 2019 13:27:00. As a result, documentation below may be outdated.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

No 'How to Run the Solution' section available. Please consider contributing.