CODEWITHSUNDEEP
prolog
Jake y
Jake y

Reputation: 59

prolog error from classifying a subclass of an atom

I'm still learning prolog but am coming across this error.

Warning: /usr/local/home/jay275/SDRIVE/cs3500/hw7/part1.pl:23:
    Clauses of bird/1 are not together in the source-file
      Earlier definition at /usr/local/home/jay275/SDRIVE/cs3500/hw7/part1.pl:10
      Current predicate: animal/1
      Use :- discontiguous bird/1. to suppress this message

I'm trying to say that if hawk then it is a bird. If it's a bird then it's a animal... etc..

Here is my code:

cat(sylvester).
cat(felix).

dog(spike).
dog(fido).

primate(george).
primate("king kong").

bird(tweety).

hawk(tony).

fish(nemo).

%then Mammal if cat or dog or primate
mammal(X) :- cat(X) ; dog(X) ; primate(X).

%then Animal if mammal or bird or fish
animal(X) :- mammal(X) ; bird(X) ; fish(X).

%then bird if hawk
bird(X) :- hawk(X).

EDIT: I don't think this error is actually causing any issues, but I'm just making sure I'm not doing anything incorrect.

EDIT2: TAS answered my question by placing the following code together.

bird(tweety).

%then bird if hawk
bird(X) :- hawk(X).

hawk(tony).

Upvotes: 3

Views: 89

Answers (1)

tas
tas

Reputation: 8140

The message informs you that the clauses of your predicate bird/1 are at different positions in your source file, namely line 10 (bird(tweety).) and line 23 (bird(X) :- hawk(X).). There are clauses of other predicates between those two lines (hawk/1, fish/1, mammal/1, animal/1), hence the definition of bird/1 is discontiguous.

The standard, ISO/IEC 13211-1:1995, states on clauses:

7.4.3 Clauses

[...]

All the clauses for a user-defined procedure P shall be
consecutive read-terms of a single Prolog text unless there
is a directive discontiguous(UP) directive indicating P
in that Prolog text.

So that leaves you with two options:

1) You add the suggested directive to your source file:

:- discontiguous bird/1.

cat(sylvester).
cat(felix).
.
.
.

2) You alter your source file such that the clauses of bird/1 appear in consecutive lines:

cat(sylvester).
cat(felix).

dog(spike).
dog(fido).

primate(george).
primate("king kong").

bird(tweety).
%then bird if hawk          % <- moved here from the end of source file
bird(X) :- hawk(X).         % <- moved here from the end of source file

hawk(tony).

fish(nemo).

%then Mammal if cat or dog or primate
mammal(X) :- cat(X) ; dog(X) ; primate(X).

%then Animal if mammal or bird or fish
animal(X) :- mammal(X) ; bird(X) ; fish(X).

Upvotes: 2

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