iseqv.java

来自「A framework written in Java for implemen」· Java 代码 · 共 56 行

package gnu.kawa.functions;
import gnu.math.*;
import gnu.mapping.*;
import gnu.text.Char;
import gnu.expr.*;

/** Implement that standard Scheme function "eqv?". */

public class IsEqv extends Procedure2 implements CanInline
{
  Language language;
  IsEq isEq;

  public IsEqv(Language language, String name, IsEq isEq)
  {
    this.language = language;
    this.isEq = isEq;
    setName(name);
  }

  public static boolean apply (Object arg1, Object arg2) 
  {
    if (arg1==arg2)
      return true;
    if (arg1 instanceof Char || arg1 instanceof Numeric
        // Symbols can now be equals even if not ==, due to namespace support.
        || arg1 instanceof Symbol)
      return arg1.equals (arg2);
    return false;
   }

  public Object apply2 (Object arg1, Object arg2)
  {
    return language.booleanObject(apply(arg1, arg2));
   }

  private static boolean nonNumeric(Expression exp)
  {
    if (exp instanceof QuoteExp)
      {
        Object value = ((QuoteExp) exp).getValue();
        return ! (value instanceof Numeric || value instanceof Char
                  || value instanceof Symbol);
      }
    return false;
  }

  public Expression inline (ApplyExp exp, ExpWalker walker)
  {
    Expression[] args = exp.getArgs();
    if (nonNumeric(args[0]) || nonNumeric(args[1]))
      return new ApplyExp(isEq, args);
    return exp;
  }
}