toint.java

来自「SRI international 发布的OAA框架软件」· Java 代码 · 共 99 行

package com.sri.oaa2.icl;

/**
 * Objects of this class convert IclTerms to ints, if possible.  Thus, this
 * works for IclInt and IclFloat.  If you don't want to implicitly convert
 * IclFloats to ints, first check if the IclTerm is an IclInt using
 * IclTerm.isInt().
 */
public final class ToInt implements OaaPrologVisitor
{
  /// Our singleton instance
  private static final ToInt singleton = new ToInt();

  protected ToInt() 
  {
  }

  public final Object visit(IclTerm node, Object data) 
  {
    return null;
  }
  
  public final Object visit(IclStruct node, Object data) 
  {
    return null;
  }
  
  public final Object visit(IclList node, Object data) 
  {
    return null;
  }
  
  public final Object visit(IclGroup node, Object data) 
  {
    return null;
  }
  
  public final Object visit(IclInt node, Object data) 
  {
    return node.toInteger();
  }
  
  public final Object visit(IclFloat node, Object data) 
  {
    return new Integer(node.getValue().intValue());
  }
  
  public final Object visit(IclStr node, Object data) 
  {
    return null;
  }
  
  public final Object visit(IclVar node, Object data) 
  {
    return null;
  }
  
  /**
   * Get an instance of a ToInt object.  This avoids multiple calls to the constructor.
   * ToInt is thread safe.
   */
  public final static ToInt getInstance() 
  {
    return singleton;
  }

  /**
   * Convert an IclTerm to an int, if possible.  If not, return the given default.
   *
   * @param IclTerm t: the term to convert
   * @param int def: the default to use
   * @return int: the IclTerm as an int, or the default value
   */
  public final int from(IclTerm t, int def) 
  {
    Integer i = (Integer)t.accept(this, null);
    if(i == null) {
      return def;
    }
    return i.intValue();
  }

  /**
   * Convert an IclTerm to an int, if possible.  If not, throw an UnsupportedOperationException.
   *
   * @param IclTerm t: the term to convert
   * @return int: the term as an int
   * @throws UnsupportedOperationException if no such conversion possible
   */
  public final int from(IclTerm t) throws UnsupportedOperationException
  {
    Integer i = (Integer)t.accept(this, null);
    if(i == null) {
      throw new UnsupportedOperationException("ToInt not supported by " + OaaPrologParser._tokenNames[t.getType()]);
    }
    return i.intValue();
  }  
}