public class IfStmt extends Statement
  {
  public Expression premise;
  public Statement conclusion;
  public Statement alternative;

  public IfStmt(Range r, Expression p, Statement c, Statement a) 
    { super(r); premise = p; conclusion = c; alternative = a; }
  public String toString()
    {
    String as = (alternative == null ? "null" : "Else," + alternative.toString());
    return "(" + tag() + " label:" + label + "," + premise + "," + conclusion + "," + as + ")";
    }

  public void visit() throws SemanticException
    { 
    label = Global.nextLabel(); 
    premise.visit(); 
    conclusion.visit(); 
    if (alternative != null) alternative.visit(); 
    }
  }