A couple questions about a simple project

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On Monday, 17 August 2015 at 15:05:56 UTC, Andre Polykanine wrote:
> Hi everyone,
> I'm  new to D (I'm learning it by reading the great online book 
> by Ali
> Çehreli  -  thank  you  very  much for it, sir!), and, more 
> than that,
> programming  is  my hobby, so please bear with me if I'm asking 
> stupid
> questions.
> I've  made  a  toy  project  which  is  a small command-line 
> XML files
> validator:
> https://github.com/Oire/dxv/
> and I have a couple questions about it:
> 1.  I'm  using std.getopt but don't know how to make it display 
> a help
> message if no options are present at all:
> D:\repos\git\dxv\dxv.exe
> (nothing   happens   but   I   would  like it to show the help 
> as with
> --help switch)
> 2. As you can see, I check whether the file to validate can be 
> read. I
> tried both `try...catch` and `enforce` (current version:
> `string  s  =  enforce(cast(string)std.file.read(f),  "Unable  
> to read
> file");`
> ),  but  this  very  exception  for  some reason can be caught 
> only in
> `main()`.
> What am I missing?
> Thanks!

1. getopt modifies args array leaving not processed arguments in 
it, i.e. name of the program and positional arguments (those 
without leading - or --). If there're no command line arguments 
given, args array will contain the only one element - the name of 
executable. Therefore you can check for args.length == 1 after 
processing by getopt.

2. catch can handle only exception of type specified in its 
argument and derived. std.file.read throws FileException on fail, 
while you catch only CheckException. To cover all cases you can 
catch any exception by using Exception type (it's the base class 
for all exception classes), or write two catch-statements in a 
row for both FileException and CheckException.

You don't need enforce here, unless you want to check if 
std.file.read returns null slice.