Hi all, I'm using program_options to combine arguments from the command line, the environment, and one or more input files. As you'd expect, it works very well. However, I have an additional requirement that I'm unsure how to implement cleanly atop the library: Given instances of program_options::options_description and program_options::variables_map, I'd like to save a program_options::parse_config_file-friendly file containing the final values obtained. Such a config file could be given back to the program and would identically reproduce the options used. The need is for some scientific software where I want a precise record of what a user has chosen for reasons of scientific repeatability. I see several ways to go about achieving this need, but all of them are ugly, brittle hacks: 1) Accessing the information directly from variables_map seems difficult due to variables_map's use of type erasure and the fact that it does not save the tokens from which values are derived. 2) Obtaining the tokens from the intermediate program_options::parsed_options instances is a possibility but requires me to effectively reimplement the logic contained within program_options::store. It also fails to account for defaulted values. 3) Looping over each program_options::value_semantic found in the options_description instance and adding a notify() callback again runs into type erasure troubles. 4) Adding a notify() to each option_description at its point of declaration avoids type erasure but makes the code impact O(n) where n is the number of options. Has anyone built such a feature atop program_options? Can anyone lend some wisdom? Thanks, Rhys