• C

Another C string conversion question

You have provided me with the answer to my last question->
How to convert integers to roman numerals (ie input: 25 output: 25 = XXV), but how do I the reverse? (ie input: XXV output: XXV = 25)

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Commented:
It looks like your homework. eh?

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Commented:
50 points ? You skinflint.
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Author Commented:
If you can't answer the question, then just say so. But I will increase the number of points to 100, as an added incentive.
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Commented:
char ch;
int thousands = 0;
int fivehundreds = 0;
int hundreds = 0;
int fities = 0;
int tens = 0;
int fives = 0;
int ones = 0;
int total = 0;
while ((ch = getc(stdin)) != EOF) {
ch = toupper(ch);
switch (ch) {
case 'M': thousands+=1000; break;
case 'D': if (hundreds>0) hundreds = -hundreds; fivehundreds+=500; break;
case 'C': hundreds+=100; break;
case 'L': if (tens>0) tens = -tens; fifties+=50; break;
case 'X': tens+=10; break;
case 'V': if (ones>0) ones = -ones; fives+=5; break;
case 'I': ones+=1; break;
}
}
total = thousands+fivehundreds+hundreds+fifties+tens+fives+ones;

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Commented:
MCMXCIX
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Commented:
Oops

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Commented:
Try this then...

switch (ch) {
case 'M': if (hundreds>0) hundreds = -hundreds; thousands+=1000; break;
case 'D': if (hundreds>0) hundreds = -hundreds; fivehundreds+=500; break;
case 'C': if (tens>0) tens = -tens; hundreds+=100; break;
case 'L': if (tens>0) tens = -tens; fifties+=50; break;
case 'X': if (ones>0) ones = -ones; tens+=10; break;
case 'V': if (ones>0) ones = -ones; fives+=5; break;
case 'I': ones+=1; break;
}

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Commented:
I've been trying to find a definitive ruling on whether
IC or VL or CMCM are legal roman numerals,
but I have been unable to find anything either forbiding or permitting them.
Does anyone know for sure, or can anyone cite a reference?
Some sources, while not saying whether thise forms are legal,
do give explicit rules for evaluating roman numerals,
which if applied to those forms give different results from the above code.
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Commented:
Try this then...

switch (ch) {
case 'M': if (fivehundreds>0) fivehundreds = -fivehundreds;
case 'D': if (hundreds>0) hundreds = -hundreds;
case 'C': if (fifties>0) fifties = -fifties;
case 'L': if (tens>0) tens = -tens;
case 'X': if (fives>0) fives = -fives;
case 'V': if (ones>0) ones = -ones;
}
switch (ch) {
case 'M': thousands+=1000; break;
case 'D': fivehundreds+=500; break;
case 'C': hundreds+=100; break;
case 'L': fifties+=50; break;
case 'X': tens+=10; break;
case 'V': fives+=5; break;
case 'I': ones+=1; break;
}

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Commented:
That last comment wan't meant to criticize the code,
(which should work to reverse anything a reasonable interger to roman conversion would produce)
so much as to ask about exactly what stings are valid as roman numerals.
Is IXC a roman numeral?
BTW, IVIX, (if it's a roman numeral) would be 13 by every source I can find.
But I can't find a source the tells me whether or not it is a roman numeral.
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