optparse-applicative is a haskell library for parsing options on the command line, and providing a powerful applicative interface for composing them. optparse-applicative takes care of reading and validating the arguments passed to the command line, handling and reporting errors, generating a usage line, a comprehensive help screen, and enabling context-sensitive bash, zsh, and fish completions. A value of type Parser a represents a specification for a set of options, which will yield a...