[fpc-pascal] Re: StrUtils.RomanToInt oddities

[Reinier Olislagers]

On 18/09/2013 16:19, Bart wrote:
> RomanToInt acceps rather ludicrous values:
> 
> RomanToInt('MDCLXVIVXLDM') = 2209
> RomanToInt('IIIIM') = 1002  //calculated as 3 + (1000-1)
> 
> Both examples represent invalid roman numbers by any standard.
> Also I do not think Roman numerals can be negative...
> 
> Feature or bug?
> 

1. I'll respond with the expected answer: "What does Delphi do" (if it
has this function?
2. I wouldn't be bothered by negative numbers... even the Romans used to
have negative posessions (= debts) and they didn't have double entry
bookkeeping yet ;) Also, the documentation [1] mentions it as a feature.
3. The rest... well, depending on 1. I'd agree it's a bug.
[1] mentions "Invalid characters are dropped from S"... which I think is
a bit strange (S is a const) but assuming it means "Invalid characters
in S are ignored" it means somebody thought checking the input for valid
Roman numbers was a good idea. The question however becomes "what is the
algorithm for deciding invalid characters" which IMO will become a mess
very quickly. Much better to just consider the entire input as invalid.

[1] http://lazarus-ccr.sourceforge.net/docs/rtl/strutils/romantoint.html