[boost] program_options lib: how to denote return values?

From: Chuck Messenger (chuckm_at_[hidden])
Date: 2003-05-22 15:20:22

Rob Stewart wrote:
> From: "James Curran" <jamescurran_at_[hidden]>
>>Chuck Messenger wrote:
>>
>>>>* add_options() should use references rather than pointers
>>
>>>"Pointer for return value" is C semantics.  In C++,
>>>pointers denote optional values.  Non-const references are for return
>>>values.
>>
>>    I disagree *strongly*.   In C and C++, the address-of syntax clearly
>>indicates that this is a value that will be changed.  Your suggestion of
>>using a non-const reference would require me to check the header file to
>>find the signature of _every_single_F#$^%ing_function to figure out which
>>parameters are changed and which one's aren't.  (particularly in the case of
> 
> Disagree strongly all you want, but I only use pointers to
> indicate optional arguments and to pass references (general
> meaning of the word) to objects that are expected to outlive the
> object to which they are given (usually in the ctor).  In the
> former case, the argument may be null so I check for that case.
> In the latter, I often use RCSPs, but not always.
> 
> I don't use non-const reference parameters often (and when I do
> they are always the first argument(s)).  I find they work
> intuitively.  You see, such functions always indicate, by their
> very name, that they are providing a value, so the name quite
> reasonably documents the output parameter.
> 
> Using pointers in this context would be counterintuitive to me.
> 
> Ultimately, someone will be disappointed.

OK, how about this syntax, to make it much more clear what is being 
returned (and, at the same time, to reduce the verbiage):

     desc.add_options()
         ...
         (param("magic|value|magic value for the program") >> magic)
         (param("val||some value with a default", defaultValue) >> val)
         ...
         ;

I've combined all 3 strings into one argument. Why have 3? It just takes 
up space. The 3 strings are separated by | (or pick a better seperator 
char).  param() is a template function.  I haven't tested this, but it 
seems like it could be made to work...

     - Chuck