How do you join characters in a list together in Prolog?

Question

Eg: ["c","h","a","r"] should print "char".

its atomic_list_concat(), but how would I do it for eg:

longest_common_prefix([H1,H2|T], P) :-
    maplist(append(P), L, [H1,H2|T]).

By writing a predicate to do that... – Willem Van Onsem Nov 25 '17 at 14:30 — Willem Van Onsem, Nov 25 '17 at 14:30

score 5 · Answer 1 · answered Nov 25 '17 at 16:27

5

Using library(double_quotes) as described here, we can use append/2 (note the 2!) :

?- set_prolog_flag(double_quotes).
   true.

?- append(["c","h","a","r"], Cs).
   Cs = "char".

However, please note that "c" is not a character! It is a list with one character. One single character is c alone. And most of the times, you do not need to write "c"

?- [c,h,a,r] = "char".
   true.

answered Nov 25 '17 at 16:27

false

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Thanks, all this time I have been thinking "c" is a character! – blazing Nov 25 '17 at 18:04

score 1 · Answer 2 · answered Nov 25 '17 at 14:33

1

in SWI-Prolog

?- atomic_list_concat( ["c","h","a","r"] , L).
L = char.

but things become hairier soon... you should take the time to learn about elementary data representation for anything serious

answered Nov 25 '17 at 14:33

CapelliC

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thanks, the problem is i dont know how to use it for my predicate, i'm new to Prolog. Any ideas? – blazing Nov 25 '17 at 14:37
just obvious ones... out the call where required, into your rule body – CapelliC Nov 25 '17 at 14:39

How do you join characters in a list together in Prolog?

2 Answers2