expression.java

用Java实现的编译器。把源代码编译成SPARC汇编程序

// $Id: Expression.java,v 1.6 1999/11/23 01:46:18 deberg Exp $

package java6035.tools.IR;

/**
 * Represents a right hand side compound expression, such as "x+y".
 */

public abstract class Expression extends IRObject 
                                 implements Rhs, Walkable
{
    protected static final int OP_EXPR = 0;
    protected static final int ALLOC_EXPR = 1;
    protected static final int ARRAY_EXPR = 2;
    protected static final int CALL_EXPR = 3;
    protected static final int VAR_EXPR = 4;
    protected static final int IMMED_EXPR = 5;

    protected abstract int expkind();

    /** 
     * Returns true if expression is an OpExpr object, false otherwise.
     */
    public boolean isOpExpr()
    {
	return expkind() == OP_EXPR;
    }

    /** 
     * Returns true if expression is an AllocExpr object, false otherwise.
     */
    public boolean isAllocExpr()
    {
	return expkind() == ALLOC_EXPR;
    }

    /** 
     * Returns true if expression is an ArrayExpr object, false otherwise.
     */
    public boolean isArrayExpr()
    {
	return expkind() == ARRAY_EXPR;
    }

    /** 
     * Returns true if expression is an CallExpr object, false otherwise.
     */
    public boolean isCallExpr()
    {
	return expkind() == CALL_EXPR;
    }

    /** 
     * Returns true if expression is an VarExpr object, false otherwise.
     */
    public boolean isVarExpr()
    {
	return expkind() == VAR_EXPR;
    }

    /** 
     * Returns true if expression is an CallExpr object, false otherwise.
     */
    public boolean isImmedExpr()
    {
	return expkind() == IMMED_EXPR;
    }

    public String PPrint(int indent, boolean recursive)
    {
        String output = new String();

        for(int i=0;i<indent;i++) output += " ";
        output += "PPrint of expressions not supported\n";
        return output;
    }
}