How to Convert Arabic Numerals to Roman Numerals with Bash

Converting Arabic numerals (the numbers we commonly use, such as 1, 2, 3, etc.) to Roman numerals may seem like a complex operation at first glance. However, with Bash, one of the most used scripting languages ​​in Linux/Unix environments, we can create a simple script that automates this process. In this article, we will see how to do it.

First of all, a brief introduction to Roman numerals. The main symbols are:

The main rules for conversion are:

• A larger symbol preceding a smaller one is added (e.g. VI = 6, XV = 15).
• A smaller symbol preceding a larger one is subtracted (e.g. IV = 4, IX = 9).

The script we will write will be based on a simple table that maps Arabic numbers to their Roman equivalents and will proceed by repeatedly subtracting the largest possible values ​​until the conversion is complete.

1. Conversion table: We create an array that contains the Arabic numbers and their corresponding Roman symbols.
2. Conversion loop: Using a while loop, we subtract the largest possible value from the number to be converted and add the corresponding Roman symbol to the result.

#!/bin/bash

# Function for converting Arabic numbers to Roman numbers
function arabic_to_roman() {
  # We define the correspondences between Arabic and Roman numbers
  local -a values=(1000 900 500 400 100 90 50 40 10 9 5 4 1)
  local -a numerals=("M" "CM" "D" "CD" "C" "XC" "L" "XL" "X" "IX" "V" "IV" "I")

  # Get the number to convert
  local num=$1
  local result=""

  # Iterate through the array of values ​​and convert
  for i to "${!values[@]}"; do
    while (( num >= values[i] )); do
      result+="${numerals[i]}"
      (( num -= values[i] ))
    done
  done

  echo "$result"
}

# Check if the user provided a number as an argument
if [[ $# -eq 0 ]]; then
  echo "Usage: $0 <number>"
  exit 1
fi

# Check if the argument is a valid number
if ! [[ $1 =~ ^[0-9]+$ ]]; then
  echo "Error: provide a positive integer."
  exit 1
fi

# Run the function with the number provided by the user
arabic_to_roman "$1"

Code explanation:

1. Conversion tables definition: We have two arrays, values and numerals, which contain the Arabic numerals and the corresponding Roman symbols respectively. For example, 1000 maps to "M", 900 to "CM", and so on.

2. arabic_to_roman function: This function takes the number to convert as an argument. The for loop iterates through all the values ​​in the array and subtracts the largest values ​​from the number as far as possible, adding the corresponding roman symbols to the result.

3. Input validation: Before performing the conversion, the script checks whether the user has provided an argument and whether the argument is a positive integer. If the input is invalid, the script prints an error message.

Considerations:

1. Number ranges: Classical Roman numerals are primarily used to represent numbers up to a few thousand. With our approach, we can handle numbers up to about 3999. If you want larger numbers, you should consider using a different notation (such as Roman numerals with slashes to indicate multiplications by 1000).

2. Negative values ​​and zeros: Roman numerals do not have a representation for zero or negative numbers. Therefore, it is advisable to add a check to handle these cases.

Conclusion

The conversion from Arabic to Roman numerals can be easily done with a Bash script, using arrays to map the values ​​and a while loop to subtract and construct the Roman numeral. This approach is simple and can be extended or modified to suit specific needs. With a few commands, we can create a useful tool in Linux environments to automate number conversion.