Question

我正在尝试读取输入文件的名称argv [1]。这就是我到目前为止所做的：

val args = CommandLine.arguments() ;
val (x::y) =  args ;
val _ = agora x

但我不断收到此错误消息：

uncaught exception Bind [nonexhaustive binding failure] .

有人可以帮忙吗？提前谢谢！

Answer 1

这是编译器警告您无法确定绑定模式是否始终存在。

例如，给定以下程序：

id

编译并运行它会给出：

SELECT CONCAT(tbl_persons.name,' ',tbl_persons.last_name,' ',tbl_persons.last_sname) as fullname, tbl_appointment.*
FROM tbl_appointment
INNER JOIN tbl_persons ON tbl_persons.idpersons = tbl_appointment.idemployee 
INNER JOIN tbl_persons ON tbl_persons.idpersons = tbl_appointment.idclient
WHERE idclient= '$user';

为了安全地处理可变数量的命令行参数，您可以使用 case-of ：

val args = CommandLine.arguments ()
val (x::y) = args
val _ = print (x ^ "\n")

编译并运行它会给出：

$ mosmlc args.sml
$ ./a.out Hello
Hello
$ ./a.out
Uncaught exception:
Bind

附注：C＆＃39 {s} fun main () = case CommandLine.arguments () of [] => print ("Too few arguments!\n") | [arg1] => print ("That's right! " ^ arg1 ^ "\n") | args => print ("Too many arguments!\n") val _ = main ()的等价物是$ mosmlc args2.sml $ ./a.out Too few arguments! $ ./a.out hello That's right! hello $ ./a.out hello world Too many arguments!。

在SML中读取命令行参数

1 个答案: