BinaryExpr.java

package jp.ac.aiit.jointry.services.lang.ast;

import java.util.List;
import jp.ac.aiit.jointry.services.lang.parser.Environment;
import jp.ac.aiit.jointry.util.JoinTryException;

public class BinaryExpr extends ASTList {

    public BinaryExpr(List<ASTree> c) {
        super(c);
    }

    public ASTree left() {
        return child(0);
    }

    public String operator() {
        return ((ASTLeaf) child(1)).token().getText();
    }

    public ASTree right() {
        return child(2);
    }

    public Object eval(Environment env) {
        String op = operator();
        if ("=".equals(op)) {
            Object right = ((ASTree) right()).eval(env);
            return computeAssign(env, right);
        }
        Object left = ((ASTree) left()).eval(env);
        Object right = ((ASTree) right()).eval(env);
        return computeOp(left, op, right);
    }

    protected Object computeAssign(Environment env, Object rvalue) {
        ASTree l = left();
        if (l instanceof Name) {
            env.put(((Name) l).name(), rvalue);
            return rvalue;
        } else {
            throw new JoinTryException("bad assignment", this);
        }
    }

    protected Object computeOp(Object left, String op, Object right) {
        if (left instanceof Integer && right instanceof Integer) {
            return computeNumber((Integer) left, op, (Integer) right);
        }

        if (op.equals("+")) {
            return String.valueOf(left) + String.valueOf(right);
        }

        if (op.equals("==")) {
            if (left == null) {
                return right == null ? TRUE : FALSE;
            } else {
                return left.equals(right) ? TRUE : FALSE;
            }
        }

        if (op.equals("!=")) {
            if (left == null) {
                return right == null ? FALSE : TRUE;
            } else {
                return left.equals(right) ? FALSE : TRUE;
            }
        }
        throw new JoinTryException("bad type", this);
    }

    protected Object computeNumber(Integer left, String op, Integer right) {
        int a = left.intValue();
        int b = right.intValue();
        if (op.equals("+")) {
            return a + b;
        }
        if (op.equals("-")) {
            return a - b;
        }
        if (op.equals("*")) {
            return a * b;
        }
        if (op.equals("/")) {
            return a / b;
        }
        if (op.equals("%")) {
            return a % b;
        }
        if (op.equals("==")) {
            return a == b ? TRUE : FALSE;
        }
        if (op.equals(">")) {
            return a > b ? TRUE : FALSE;
        }
        if (op.equals("<")) {
            return a < b ? TRUE : FALSE;
        }
        if (op.equals(">=")) {
            return a >= b ? TRUE : FALSE;
        }
        if (op.equals("<=")) {
            return a <= b ? TRUE : FALSE;
        }
        if (op.equals("!=")) {
            return a != b ? TRUE : FALSE;
        }

        throw new JoinTryException("bad operator", this);
    }
}