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60. Convert a Roman Numeral

Description

Converts a Roman numeral back into a standard (Arabic) number.

Code

SET TextVar TO "«TextVar:LIKE THIS»"
SET Temp-n TO LENGTH( TextVar )
SET LoopLimit-n[ Temp-n ] TO 1

0
REPEAT Loop

// Look at the next two characters
SET Char-t TO MID( TextVar, COUNTER, 1 )
IF COUNTER < Temp-n
SET Next-t TO MID( TextVar, COUNTER + 1, 1)
ELSE
SET Next-t TO ""
END IF

// 1s
IF Char-t = "I"
IF Next-t = "V"
OR Next-t = "X"
OR Next-t = "L"
OR Next-t = "C"
OR Next-t = "D"
OR Next-t = "M"
RESULT - 1
ELSE
RESULT + 1
END IF

// 5s
ELSE IF Char-t = "V"
IF Next-t = "X"
OR Next-t = "L"
OR Next-t = "C"
OR Next-t = "D"
OR Next-t = "M"
RESULT - 5
ELSE
RESULT + 5
END IF

// 10s
ELSE IF Char-t = "X"
IF Next-t = "L"
OR Next-t = "C"
OR Next-t = "D"
OR Next-t = "M"
RESULT - 10
ELSE
RESULT + 10
END IF

// 50s
ELSE IF Char-t = "L"
IF Next-t = "C"
OR Next-t = "D"
OR Next-t = "M"
RESULT - 50
ELSE
RESULT + 50
END IF

// 100s
ELSE IF Char-t = "C"
IF Next-t = "D"
OR Next-t = "M"
RESULT - 100
ELSE
RESULT + 100
END IF

// 500s
ELSE IF Char-t = "D"
IF Next-t = "M"
RESULT - 500
ELSE
RESULT + 500
END IF

// 1000s
ELSE IF Char-t = "M"
RESULT + 1000
END IF

SET LoopLimit-n TO UNANSWERED
END REPEAT
SET Temp-n TO UNANSWERED
SET Char-t TO UNANSWERED
SET Next-t TO UNANSWERED

Explanation

This computation is for the rare occasion when you need to convert a Roman numeral back into a standard numeral (e.g. "MCMXCIX" > 1999). The result is a HotDocs number value.

NOTE: To format a standard numeral as a Roman numeral, just use the "IX" format for the number.

This computation uses a simple loop in the form of a repeated dialog called Loop. A detailed explanation of how the loop works is available in Computation 15: Loops Via REPEAT. The dialog has a single number variable in it called LoopLimit-n. Set this variable's Advanced options to "Ask only in dialog," "Don't warn if unanswered," and "Don't save in answer file." The computation also uses two other temporary text variables, Char-t and Next-t. Set their Advanced options just like you did for LoopLimit-n. These variables store the current characters being analyzed.

The computation uses the Loop to examine each character of the Roman numeral, one at a time. On any given pass, the computation will store the current character in Char-t and the character following it (if any) in Next-t. We do this because we must see two Roman numerals at a time, as you'll see.

The computation then examines the character in Char-t to determine what it is. It must then look at the following character to see if it is higher in order. If so, the current character is reducing the overall value. Otherwise it is increasing it. For example, the character "I" normally increases the overall value by 1 (e.g. VI = 5 + 1, or 6; VIII = 5 + 1 + 1 + 1, or 8). But if a higher-order character follows it, it reduces the overall value by 1 (e.g. IV = -1 + 5, or 4; IX = -1 + 10, or 9).

The computation returns the numeric equivalent of the Roman numeral

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