I don't know what happens when the substring overlaps. Like for the number 6, will it replace the first 5 I's with V and end up correctly with VI or the last ones and come to IV? I would guess the former and maybe you know but I never thought about it before

[–] Atlas_@lemmy.world 6 points 10 months ago (1 children)

Also does not handle 'IIIIIIIII' -> 'IX' properly

[–] pitiable_sandwich540@feddit.org 2 points 10 months ago (1 children)

If the substitution went right to left it might work.

[–] rooroo@feddit.org 2 points 10 months ago

It does.

[–] rooroo@feddit.org 2 points 10 months ago (1 children)

I’ve written it that way and it works, as in it will replace left to right and you replace iiii to iv after iiiii to v

[–] lugal@lemmy.dbzer0.com 0 points 10 months ago (1 children)

Makes sense but it will fail at 9 (VIV) it would only work for 9 if the replace went from right to left or the V and IV statements were exchanged but in both cases, 6 would fail

[–] rooroo@feddit.org 1 points 10 months ago (1 children)

9 is IX though, and that works.

6 works fine, as it replaces the first set of 5 I with V and then there’s nothing to replace.

I’d written it in typescript for all it’s worth; go ahead and try it yourself :)

[–] lugal@lemmy.dbzer0.com 1 points 10 months ago (2 children)

Does 9 really work? Wouldn't it be:

IIIIIIIII
-> VIIII
-> VIV

[–] rooroo@feddit.org 2 points 10 months ago (2 children)

No, cause you do the replacement from large to small, I.e. you’d first check for 10 I to replace with X (none found); then replace 9 with IX (check), then check for 5, 4 and so on.

[–] lugal@lemmy.dbzer0.com 2 points 10 months ago (1 children)

The original doesn't have an extra check for 9 and it works for Roman->Indioarabic because it's:

IX
->IVV
->IIIIV
->IIIIIIIII

But the other way around, you need an extra step for 9. That's where our misunderstanding comes from.

[–] rooroo@feddit.org 2 points 10 months ago

Ohhh haha that makes sense. Fun!

[–] rooroo@feddit.org 1 points 10 months ago

I noticed my “and so on” is literally a noop here so yeah.

[–] rooroo@feddit.org 2 points 10 months ago

I like your questions about this and they all seem fair but I kinda wanna encourage you to go ahead and write it yourself; it’s a fun way to convert into Roman numerals that both is and isn’t intuitive at the same time.