[parser::params] add overload accepting std::initializer_list

[kedartal]

Allows calling cmdl.params( { "--name", "-n" } ) and getting all relevant values, regardless of which param name was used on the command line. For example,

std::ranges::for_each(
   cmdl.params( { "--name", "-n" } ) | std::views::values,
   []( const std::string& value ) {
      // do something with the parameter value
    } );

Since the implementation uses std::ranges, perhaps it's a good idea to conditionally enable it only for c++>=20 and feature test __cpp_lib_ranges; I know some projects prefer making equivalent tests in the build system and setting a compiler definition accordingly, any thoughts?

Also, this implementation requires that the parser's lifetime exceeds that of the return value -- this gets captured in the lambda -- which to me seems natural in most use cases, and a reasonable thing to require (and document). The alternative would be making a copy of the data...

[kedartal]

Conditionally enabling the overload based on std::ranges availability.

__has_include is standard for c++>=17, #include <version> provides the __cpp_lib_ranges definition.

[adishavit]

Thank you for this - I have a super busy period - and won't be able to properly review.
Please be patient - I'll get to it.

That being said, I will say that Argh is intentionally C++11 (some original C++14 functionality/code was actively downgraded/backported) to allow broader appeal.
A C++11 conforming implementation is more likely to be accepted.

OTOH, I am considering a new version >= C++20, to allow more powerful features - bit that's still ways off.

[kedartal]

Cool, let me know if I can help with the modern version when you get around to it.