Re: I/O - exception handling

["Robert I. Eachus" <rieachus@attbi.com>]

Preben Randhol wrote:
> 
> OK understand. *I* would then do:
> 
>    procedure Safe_Close (File : File_Type)...
> 
> Now you can use the Safe_Close in any function you like.

I have "decorated" open and close routines that I keep copying around 
and using in even simple utilities because even the most minimal code to 
  open a file, check that the open succeeded, or print a diagnotic if it 
didn't runs to over a page.  But I haven't considered these things as a 
good candidate for standardization because there are just too many 
different text strings--and personal preferences--involved.

The other problem is that the open routine can't exit from the enclosing 
procedure, so after printing a diagnostic, it has to reraise the 
exception (or raise some other exception).  This is fine if the program 
can't run without an input file, but there are other cases where you 
might want to continue.  Gets complicated, but that is the nature of a 
file that may or may not exist, and may not be accessable due to 
permissions, or may be open by some other program for writing and so on.

The only conclusion I have reached is that there is no such thing as 
"simply" opening a file.