exprToPred path (UnaryOp op arg _) = do
    argp <- exprToPred (path.op_argL) arg
    return $ pUnaryOp (pOp op) argp
exprToPred path (UnaryOp op arg _) = do
    argp <- exprToPred (path.op_argL) arg
    return $ pUnaryOp (pOp op) argp
exprToPred path (UnaryOp op arg _) = do
    argp <- exprToPred (path.op_argL) arg
    return $ pUnaryOp (pOp op) argp