Usless but maybe fun excercise

ndzied1 · May 14, 2006

At breakfast this morning, my son started talking about Roman Numerals. Of course, my mind quickly wondered to how to write a PLC program to display the year, or time or any number in Roman Numerals on an HMI. Of course this is very platform dependant but issues of displaying strings have been coming up lately and I thought I'd throw it out there for the masses.

bernie_carlton · May 14, 2006

In a PLC? Interesting. One of my first programs I wrote on my first home comuputer (TRS-80) in BASIC was to input a string, determine if it was Roman Numeral, Arabic Numerals or something else, then, if one of the number formats, convert and output it as the other. A great learning experience.

Sergei Troizky · May 14, 2006

Actually, the only difference between Roman and decimal systems is the floating radix of the Roman system.

The decimal-to-Roman algorythm is not difficult and also not that useless.
The examples immediately coming in mind are:
- Composing necessary money amount from different value coins and/or bills.
- Weighing and all it's variations, including analog-to-digital conversion in electronics.

bernie_carlton · May 14, 2006

There is also the question of which mode of conversion is to be used. The Romans on their buildings most often used the purely additive form (9 = VIIII) while we now tend to see the subtractive form for avoiding more than 3 occurances of a symbol (9 = IX).

Sergei Troizky · May 14, 2006

Yes, but this is just a simple additional procedure applying to four consecutive similar symbols.
It may be considered an illegal combination of legal symbols, something like nibbles with values over 9 in BCD.
I would probably program additive-to-subtractive conversion as a second step of the conversion.
BTW, in the subtractive form symbols change their radix to negative when they are positioned before more valuable symbol, that is floating radix.
In the additive form the radix is not floating, it is just non-proportional.

Terry Woods · May 14, 2006



Assuming the number is limited to 9,999 (and neglecting the Bar-V for 5000)



String = Null



Number / 1000 = Result



If Result > 0 Then...

	- Append "Result" Ms (For example, if Result = 3, Append three Ms)

	- Number - (Result x 1000) = Number

EndIf



If Number >= 900 Then...

	- Append "CM"

	- Number - 900 = Number

ElseIf Number >= 500 Then...

	- Append "D"

	- Number - 500 = Number

ElseIf Number >= 400 Then...

	- Append "CD"

	- Number - 400 = Number

EndIf



Number / 100 = Result



If Result > 0 Then...

	- Append "Result" Cs (For example, if Result = 3, Append three Cs)

	- Number - (Result x 100) = Number

EndIf



If Number >= 90 Then...

	- Append "XC"

	- Number - 90 = Number

ElseIf Number >= 50 Then...

	- Append "L"

	- Number - 50 = Number

ElseIf Number >= 40 Then...

	- Append "XL"

	- Number - 40 = Number

EndIf



Number / 10 = Result



If Result > 0 Then...

	- Append "Result" Xs (For example, if Result = 3, Append three Xs)

	- Number - (Result x 10) = Number

EndIf



If Number = 9 Then...

	- Append "IX"

ElseIf Number >= 5 Then...

	- Append "V"

	- Number - 5 = Number

ElseIf Number = 4 Then...

	- Append "IV"

	- Number - 4 = Number

EndIf



Append "Number" Is (For example, if Number = 3, Append three Is)

marius · May 15, 2006

well... somehow like this... assume floor round and non-float division

no/1000 = m_count; no -= m_count*1000;
no/500 = d_count; no -= d_count*500;
no/100 = c_count; no -= c_count*100;
no/50 = l_count; no -= l_count*50;
no/10 = x_count; no -= x_count*10;

now we need to assemble string m_count*'M'+d_count*'D'+ .... + no*'I'
yes, just original, not classical mode

Usless but maybe fun excercise

ndzied1

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bernie_carlton

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Sergei Troizky

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bernie_carlton

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