getopt-generics tries to make it very simple to create command line
interfaces. Here's an example:
import WithCli
main :: IO ()
main = withCli run
run :: String -> Int -> Bool -> IO ()
run s i b = print (s, i, b)This is how the program behaves in a shell:
$ program foo 42 true
("foo",42,True)
$ program --help
program [OPTIONS] STRING INTEGER BOOL
-h --help show help and exit
$ program foo 42 bar
cannot parse as BOOL: bar
# exit-code 1
$ program
missing argument of type STRING
missing argument of type INTEGER
missing argument of type BOOL
# exit-code 1
$ program foo 42 yes bar
unknown argument: bar
# exit-code 1