[boost] program_options lib review

From: Tanton Gibbs (thgibbs_at_[hidden])
Date: 2003-05-22 15:23:36

I have to say that I'm a little torn over this library.  I really like its
simplicity and usefulness; however, I wish it were more of a facade on a
more complex library.  For example, I would like to be able to have multiple
config file parsers for winini, tag=value,xml, or other config file types.
Also, I would like to see canned custom parsers for -fparm/-fno-parm and
+parm -parm syntax.  However, as it stands I think it is a good contribution
and I would definitely use it.  I will withhold my vote until I have a
chance to play around with it some more.

Here are my addressable comments
(1) I would like to have a find_if and count_if function as I often want to
find a parameter of the format *.field.*  It doesn't matter what the *'s are
as long as it contains .field.  They should both take a function as a
parameter.
(2) Someone else mentioned custom parameter verification.  I'm kind of split
on this.  I don't mind it if you could pass in an arbitrary functor (like a
lambda library functor).  However, I also don't mind doing the validation
outside of the library.  I definitely don't want the parameter function to
take arbitrary parameters (like the min/max idea presented earlier) as that
would just be too confusing.
(3) As another pointed out, the documentation is definitely lacking.  I
would like less of code documentation and more of user documentation.  I
would like to see more examples with sample output and a slow moving
tutorial that covers all of the features.
(4) What if I want parameters to occur in a particular order?  For example,
the -kk option can only occur after the update parameter in cvs:
cvs update -kk blah blah blah is legal
cvs -kk update blah blah blah is not
It would be nice to either be able to specify a mandatory ordering, or to be
able to find out the position of the parameter.  If you could specify a
mandatory ordering, then I would like it to be relative.  For instance every
parameter with ordering level 0 must appear before every parameter with
ordering level 1; however, parameters with ordering level 0 can appear in
any order amongst themselves.

Now for comments on what other people have said.
(1) I also like parameter as the last argument instead of the middle
one...it just flows better to me.
(2) I like the parameter function and don't really like the syntax that used
the >> operator...it just looks odd to me.
(3) I like the parameter function taking the argument by pointer as it is
easier to understand what is happening.
(4) The exception name "error" doesn't bother me...I kinda like it :)

All in all it looks to be a good library.  However, I may have missed the
ability to define a custom config file format.  If I didn't then I fully
think that needs to be added or config files need to be dropped entirely.
Even environment variables could be used with a custom config file parser.
Also, the documentation leaves much to be desired.  If those two concerns
are addressed then I will fully support this library.

Tanton