Expr.java

package polyglot.ast;

import polyglot.types.Type;
import polyglot.util.CodeWriter;
import polyglot.visit.PrettyPrinter;

/**
 * An <code>Expr</code> represents any Java expression.  All expressions
 * must be subtypes of Expr.
 */
public interface Expr extends Receiver, Term
{
    /**
     * Return an equivalent expression, but with the type <code>type</code>.
     */
    Expr type(Type type);

    /** Get the precedence of the expression. */
    Precedence precedence();

    /**
     * Return whether the expression evaluates to a constant.
     * This is not valid until after disambiguation.
     */
    boolean isConstant();

    /** Returns the constant value of the expression, if any. */
    Object constantValue();
    
    /**
     * Correctly parenthesize the subexpression <code>expr<code>
     * based on its precedence and the precedence of this expression.
     *
     * If the sub-expression has the same precedence as this expression
     * we parenthesize if the sub-expression does not associate; e.g.,
     * we parenthesis the right sub-expression of a left-associative
     * operator.
     */
     void printSubExpr(Expr expr, boolean associative,
                       CodeWriter w, PrettyPrinter pp);

    /**
     * Correctly parenthesize the subexpression <code>expr<code>
     * based on its precedence and the precedence of this expression.
     *
     * This is equivalent to <code>printSubexpr(expr, true, w, pp)</code>
     */
    void printSubExpr(Expr expr, CodeWriter w, PrettyPrinter pp);
}