ASTAnd.java

public class ASTAnd implements ASTNode {
        ASTNode lhs, rhs;
        
        public ASTAnd(ASTNode l, ASTNode r) {
                lhs = l;
                rhs = r;
        }
        
        @Override
        public IValue eval(Environment<IValue> e) throws InterpreterError {
                IValue v1 = lhs.eval(e);

                if (!(v1 instanceof VBool))
                        throw new InterpreterError("illegal types to && operator");

                if (!((VBool)v1).getval()) // short-circuit
                        return new VBool(false);

                IValue v2 = rhs.eval(e);

                if (!(v2 instanceof VBool))
                        throw new InterpreterError("illegal types to && operator");

                return new VBool(((VBool)v2).getval());
        }

        @Override
        public ASTType typecheck(Environment<ASTType> e) throws TypeCheckError, InterpreterError {
                ASTType lhst = lhs.typecheck(e);
                ASTType rhst = rhs.typecheck(e);
                if (!(lhst instanceof ASTTBool) || !(rhst instanceof ASTTBool))
                        throw new TypeCheckError("&&: arg type not bool");
	        return ASTTBool.tbool;
	}

        @Override
        public boolean isFreeOutsideLambda(String id) {
                return lhs.isFreeOutsideLambda(id) || rhs.isFreeOutsideLambda(id);
        }

}