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Jason is a fully-fledged interpreter for an extended version of AgentSpeak, a BDI agent-oriented logic programming language.

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package jason.stdlib;

import jason.asSemantics.DefaultInternalAction;
import jason.asSemantics.InternalAction;
import jason.asSemantics.TransitionSystem;
import jason.asSemantics.Unifier;
import jason.asSyntax.Term;

/**
  Internal action: .literal.

  
Description: checks whether the argument is a literal,
  e.g.: "p", "p(1)", "p(1)[a,b]", "~p(1)[a,b]". 

  
Parameter:

  + argument (any term): the term to be checked.

  

  Examples:

   .literal(b(10)): true.
  
 .literal(b): true.
  
 .literal(10): false.
  
 .literal("Jason"): false.
  
 .literal(X): false if X is free, true if X is bound to a literal.
  
 .literal(a(X)): true.
  
 .literal([a,b,c]): false.
  
 .literal([a,b,c(X)]): false.
  

  @see jason.stdlib.atom
  @see jason.stdlib.list
  @see jason.stdlib.number
  @see jason.stdlib.string
  @see jason.stdlib.structure
  @see jason.stdlib.ground
*/
public class literal extends DefaultInternalAction {
    
    private static InternalAction singleton = null;
    public static InternalAction create() {
        if (singleton == null) 
            singleton = new literal();
        return singleton;
    }

    @Override public int getMinArgs() { return 1; }
    @Override public int getMaxArgs() { return 1; }

    @Override
    public Object execute(TransitionSystem ts, Unifier un, Term[] args) throws Exception {
        checkArguments(args);
        return args[0].isLiteral();
    }
}