Command line option parsers

There are several packages that want to simplify the task of writing command line parsers. Unfortunately, they are distributed across several Hackage categories. Here is an attempt to list them:

Package	Multi-mode	Extensions	Remark
argparser	-	None (though it depends on package containers, which uses extensions)
cmdargs	X	TemplateHaskell, SYB generics, ViewPatterns, ...	unsafePerformIO
cmdlib	X	SYB generics	based on GetOpt
cmdtheline	X	FlexibleInstances (although unnecessary)	shows help as man-page
console-program	X	(none)	configure options via files
getflag	-	Haskell98	like GetOpt but with Unix/Plan 9 option syntax
hflags	-	TemplateHaskell	inspired by Google's gflags, provides parsed options in top-level variables, allow to set options via environment variables
multiarg	-	CPP	long options with multiple arguments
options	X	TemplateHaskell
optparse-applicative	X	GADT	Applicative Functor; for wrong arguments it does not show a specific error message but the general usage pattern
parseargs	-	FlexibleInstances (although unnecessary)	supports a fixed set of argument types: Int, Integer, Float, Double, String, FileOpener
ReadArgs	-	OverlappingInstances, TypeOperators	No options, only arguments. The argument template is derived from the requested argument tuple.
simpleargs	-	OverlappingInstances (although unnecessary)	the same as ReadArgs
yaop	-	TemplateHaskell, GeneralizedNewtypeDeriving	wrapper around GetOpt

The column for required Haskell extensions gives an idea of how easy it is to port the package to compilers other than GHC.