It simply determines if the current value minus one of our pattern values multiplied by one, ten, hundred, thousand, and ten thousand. Public MustOverride Function Multiply() As Integer Public MustOverride Function NineStrings() As String Public MustOverride Function FiveStrings() As String Public MustOverride Function FourStrings() As String Public MustOverride Function OneStrings() As String Putting It All TogetherĪdd the following class: Public MustInherit Class Terminals I’ll stop here, but the same pattern applies to hundred thousands and millions. I will explain the Terminals (which this class inherits from) class a bit later. All the properties simply output the necessary string when a change should occur. Public Overrides Function Multiply() As Integer Public Overrides Function NineStrings() As String Public Overrides Function FiveStrings() As String Public Overrides Function FourStrings() As String Public Overrides Function OneStrings() As String The List that was created contains classes that will make use of the same pattern I have mentioned earlier, as you will see now.Īdd a class for multiples of One: Class Ones Interpret outputs the information with the help of the InputOutput class. Public Overrides Sub Interpret(value As InputOutput)įor Each reExp As RomanExpression In AllExpressions Private AllExpressions As New List(Of RomanExpression)() _ Add this class now: Public Class ParseDecimalToRoman Now, we need a class to format the output of Roman numbers so that it forms the correct ultimate number. Public MustOverride Sub Interpret(value As InputOutput) This class is ultimately responsible for the input of ordinary numbers and the output of Roman numbers. Now, to put this newfound knowledge of this pattern as well as understanding that we only have seven unique symbols to work with, is quite easy, but it is a lot of work. Always look long and hard at a situation you will find answers… Seeing this pattern allows you to better think of a solution. At nine, there is again a change as well as 10. Six through eight follow the same sequence as one to three. The fifth shows the unique symbol for 5, 50, 500, and so on. Then, with the fourth item, it shows the first number in the current sequence, plus the next unique symbol. The second in the sequence has two of the same symbol, and the third in the numeric sequence has three. Before I get too far ahead of myself, look at the following:Įvery sequence starts with a unique symbol as the first in the sequence, so that means 1 = I, 10 = X, 100 = C. Man, I love patterns! If you look closely, you will see the same pattern being repeated depending on what the value of the number is. Let me pause here and explain the methodology first. Feel free to use your own names, but remember that my names might be different than yours. Let’s create a project that can convert Roman Numerals to ordinary numbers.Ĭreate a new Visual Basic Windows Forms project and add one button to the form. This means that you cannot have a number written as IIII-which ordinarily would mean four-but written as IV instead.Įnough history? Okay, let me move on. Talking about the Roman number four, this number is written like that for the simple reason that four or more symbols that look the same aren’t allowed to be written out. The Roman Numeral system is additive this means that the numbers are simply added. This means then that IX equals nine, XC is ninety, and CM becomes nine hundred. The ultimate value of this letter-group, or number, equals the second letter’s value subtracted by the first letter. If two letters are next to each other, each letter is worth powers of ten and the second letter is worth ten times the first. For example: A number such as 203 is written as CCIII. There is no symbol for a zero, so there is also no need for zeros to keep place for other numbers. By combining symbols, a Roman number is formed. The Roman numerical system is composed of seven Latin letters which include: I (unus): one V (quinque): five X (decem): ten L (quinquaginta): fifty C (centum): one hundred D (quingenti): five hundred and M (mille): one thousand. This numeric system stayed the way of writing numbers in Europe until the Middle Ages. First, Some HistoryĪ Roman Numeral is a number that is written in the way that the ancient Romans used to write numbers. Today, I will show you a few different ways to create a decent Roman Numeral converter with Visual Basic. It may seem to be a relatively easy task, but looks are deceiving, indeed. A popular question on developer forums is how to create a Roman Numeral converter.
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