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

import java.util.Iterator;

/**
Internal action: .min.

    
Description: gets the minimum value of a list of terms, using
    the "natural" order of terms. Between 
different types of terms, the following order is
used:


numbers < atoms < structures < lists 

Parameters:

+   list (list): the list where to find the minimal term.

+/- minimal (term). 


Examples:


 .min([c,a,b],X): X unifies with
a.


.min([b,c,10,g,f(10),[3,4],5,[3,10],f(4)],X):
X unifies with 5.


.min([3,2,5],2): true.


.min([3,2,5],5): false.


.min([],X): false.



  @see jason.stdlib.concat
  @see jason.stdlib.delete
  @see jason.stdlib.length
  @see jason.stdlib.member
  @see jason.stdlib.nth
  @see jason.stdlib.sort
  @see jason.stdlib.max
  @see jason.stdlib.reverse

  @see jason.stdlib.difference
  @see jason.stdlib.intersection
  @see jason.stdlib.union

*/
public class min extends DefaultInternalAction {
    
    private static InternalAction singleton = null;
    public static InternalAction create() {
        if (singleton == null) 
            singleton = new min();
        return singleton;
    }

    @Override public int getMinArgs() { return 2; }
    @Override public int getMaxArgs() { return 2; }

    @Override protected void checkArguments(Term[] args) throws JasonException {
        super.checkArguments(args); // check number of arguments
        if (!args[0].isList())
            throw JasonException.createWrongArgument(this,"first argument must be a list");
    }

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

        ListTerm list = (ListTerm)args[0];
        if (list.isEmpty()) {
            return false;               
        }

        Iterator i = list.iterator();
        Term min = i.next();
        while (i.hasNext()) {
            Term t = i.next();
            if (compare(min,t)) {
                min = t;
            }
        }
        return un.unifies(args[1], min.clone());
    }
    
    protected boolean compare(Term a, Term t) {
        return a.compareTo(t) > 0;
    }
}