Haskell library that supports command-line flag processing.
Too see an user guide and list of features go to
https://github.com/josercruz01/hsoptions#table-of-contents.
Flags are declared in the code by using the make function, which takes the
flag's name, help text and type as arguments.
The flags are parsed from the command line stream of from a file
if the --usingFile <filename> flag is sent to the program.
Flags can be customized by calling configuration function, such as
defaultIs or aliasIs, that change how the flag behaves, how it
is parsed and validated.
The processMain function needs to be called at the beginning of the main
function. This function takes as arguments:
The program description
A list of all declared flags
Three callbacks:
* success
* failure
* display help
If there is any kind of validation error failure is
called with the list of errors. If the --help flag was sent by the user
display help is called. Otherwise if there are no problems the success
function is called.
A default implementation of failure and display help is provided in the
library (defaultDisplayHelp, defaultDisplayErrors) with a basic bahavior.
Basically success becomes the 'real' main function. It takes as argument
a tuple (FlagResults, ArgsResults). FlagResults is a data structure
that can be used to query flags by using the get function. ArgsResults is
just an array of String containing the remaining not-flag arguments.
A simple example (more in
https://github.com/josercruz01/hsoptions/tree/master/examples)
At the processMain function each of the input flags is validated against the
declared flags. Within the success function you can be sure that all required
flags exist, all flag types are correct and all validation was successful.