Hodgepodge

Problem Description

1. Ask the user to enter a number in roman numerals.
2. Convert the number to a decimal value.
3. Output the decimal value.
4. Output an error message if the roman numeral is not in the correct form.
5. Go to step 1. (Continue until the user indicates they want to quit.)

Desigh Suggestions

1. Put the string conversion code in a function.
2. Convert lowercase input characters to uppercase for processing and displaying.

Links

Roman numerals (Wikipedia)

RegEx Roman Numerals - Computerphile

Miscellaneous

Roman Numeral	Value
I	1
II	2
III	3
IV	4
V	5
VI	6
VII	7
VIII	8
VIIII	9

Symbol	Value
I	1
V	5
X	10
L	50
C	100
D	500
M	1,000

Example	Value
MCDXCII	1492
MMXX	2020
MCMXLIV	1944
XCIX	99

Rules

Rules for writing roman numerals from www.cuemath.com/numbers/roman-numerals/

The letters I, X, C can be repeated thrice in succession. Additionally, L, V, D cannot be repeated or the number is considered to be invalid.
If a lower value digit is written to the left of a higher value digit, it is subtracted.
If a lower value digit is written to the right of a higher value digit, it is added.
Only I, X, and C can be used as subtractive numerals.