code: /**
   * Copyright (c) 2005, Regents of the University of California
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * Redistributions of source code must retain the above copyright notice,
   * this list of conditions and the following disclaimer.
   *
   * Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * Neither the name of the University of California, Los Angeles nor the
   * names of its contributors may be used to endorse or promote products
   * derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * Creation date: Oct 4, 2005
   */
  
  package jintgen.jigir;
  
  import cck.parser.SourcePoint;
  import jintgen.isdl.parser.Token;
  import jintgen.types.*;
  
  /**
   * The <code>BinOp</code> inner class represents an operation on two integers with an infix binary
   * operation. For example, addition, multiplication, bitwise and, and such operations are binary infix and
   * therefore subclasses of this class.
   */
  public class BinOpExpr extends Expr {
      /**
       * The <code>operation</code> field stores the string name of the operation of this binary operation.
       * For example, '+' represents addition.
       */
      public final Token operation;
  
      /**
       * The <code>left</code> field stores a reference to the expression that is the left operand of the
       * binary operation.
       */
      public final Expr left;
  
      /**
       * The <code>left</code> field stores a reference to the expression that is the right operand of the
       * binary operation.
       */
      public final Expr right;
  
      /**
       * The <code>binop</code> field stores a reference to the actual binary operation that this
       * syntax tree node corresponds to.
       */
      protected BinOpImpl binop;
  
      /**
       * The constructor of the <code>BinOp</code> class initializes the public final fields that form the
       * structure of this expression.
       *
       * @param l the left expression operand
       * @param o the a token representing the name of the operation such as '+'
       * @param r the right expression operand
       */
      public BinOpExpr(Expr l, Token o, Expr r) {
          left = l;
          right = r;
          operation = o;
      }
  
      /**
       * The <code>isConstantExpr()</code> method tests whether this expression is a constant expression
       * (i.e. it is reducable to a constant and has no references to variables, maps, etc).
       *
       * @return true if this expression can be evaluated to a constant; false otherwise
       */
      public boolean isConstantExpr() {
          return left.isConstantExpr() && right.isConstantExpr();
      }
  
      /**
       * The <code>toString()</code> method recursively converts this expression to a string. For binary
       * operations, inner expressions will be nested within parentheses if their precedence is lower than
       * the precedence of the parent expression.
       *
       * @return a string representation of this expression
       */
      public String toString() {
          return innerString(left) + ' ' + operation + ' ' + innerString(right);
      }
  
      /**
       * The <code>getBinOp()</code> method returns a reference to the actual binary operation
       * represented by this abstract syntax tree node. Since all binary operations are represented
       * with the same type of syntax tree node, this field stores a reference to an implementation
       * of the actual operation (e.g. logical and or arithmetic addition).
       * @return a reference to the binary operation that this node represents
       */
      public BinOpImpl getBinOp() {
          return binop;
      }
  
      /**
       * The <code>setBinOp()</code> method sets the reference to the actual binary operation for this
       * node.
       * @param b the binary operation implementation for this node
       */
      public void setBinOp(BinOpImpl b) {
          binop = b;
      }
  
      /**
       * The <code>getPrecedence()</code> method gets the binding precedence for this expression. This is
       * used to compute when inner expressions must be nested within parentheses in order to preserve the
       * implied order of evaluation.
       *
       * @return an integer representing the precedence of this expression; higher numbers are higher
       *         precedence
       */
      public int getPrecedence() {
          if ( binop == null ) return -1;
          return binop.prec;
      }
  
      /**
       * The <code>getSourcePoint()</code> method returns a reference to a <code>SourcePoint</code>
       * instance that represents the location in the source program of this expression.
       * @return a <code>SourcePoint</code> instance that represents this expression in the
       * source program
       */
      public SourcePoint getSourcePoint() {
          return operation.getSourcePoint();
      }
  
      public SourcePoint getSourceRange() {
          return new SourcePoint(left.getSourcePoint(), right.getSourcePoint());
      }
  
      /**
       * The <code>accept()</code> method implements one half of the visitor pattern so that client visitors
       * can traverse the syntax tree easily and in an extensible way.
       *
       * @param v the visitor to accept
       */
      public void accept(CodeVisitor v) {
          v.visit(this);
      }
  
      /**
       * The <code>accept()</code> method implements one half of the visitor pattern for rebuilding of
       * expressions. This visitor allows code to be slightly modified while only writing visit methods for
       * the parts of the syntax tree affected.
       *
       * @param r the rebuilder to accept
       * @return the result of calling the appropriate <code>visit()</code> method of the rebuilder
       */
      public <Res, Env> Res accept(CodeAccumulator<Res, Env> r, Env env) {
          return r.visit(this, env);
      }
  
      /**
       * The <code>BinOpImpl</code> class represents a binary operation implementation. Descendants
       * of this class implement the functionality of a binary operator, including typechecking,
       * constant evaluation, etc.
       */
      public abstract static class BinOpImpl implements TypeCon.BinOp {
          public final String operation;
          public final int prec;
  
          protected BinOpImpl(String op, int p) {
              operation = op;
              this.prec = p;
          }
  
          public String getOperation() {
              return operation;
          }
  
          public abstract Literal evaluate(Literal left, Literal right);
          public abstract Type typeCheck(TypeEnv env, Typeable left, Typeable right);
      }
  
  }
  