CODEWITHSUNDEEP
prologdcgroman-numerals
Cole Dapprich
Cole Dapprich

Reputation: 93

How do I test if a list contains two atoms next to each other in Prolog?

I am trying to write a predicate in GNU Prolog that tests if a roman numeral, stored as a list of characters, is well formed. Namely, if the list contains [i, c], [i, m], or [x, m], it is invalid. For example, if I passed in [m, i, m], the output would be no.

How would I go about doing this? I am aware of the member/2 function; is there a way to use that to test if a list contains a sublist?

Upvotes: 2

Views: 197

Answers (2)

Cole Dapprich
Cole Dapprich

Reputation: 93

Found a built-in sublist function that does exactly what I need:

sublist([i, m], [m, i, m]) ==> `true`

Upvotes: 2

false
false

Reputation: 10102

Consider to use grammars (). And use

:- set_prolog_flag(double_quotes, chars).

which permits you to write "mcm" in place of [m,c,m]. See this answer for more.

Upvotes: 1

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