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

Question

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?

score 1 · Answer 1 · edited Apr 28 '19 at 19:07

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

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

edited Apr 28 '19 at 19:07

peterh

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answered Dec 01 '16 at 03:24

Cole Dapprich

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score 1 · Answer 2 · edited May 23 '17 at 12:30

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Consider to use grammars (dcg). 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.

edited May 23 '17 at 12:30

Community

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answered Dec 01 '16 at 11:38

false

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

2 Answers2