The type of command line arguments.

Information about an optional argument. Exposes the folowing fields.

optName

:: String: defaults to "".

optDoc

:: String: defaults to "".

optSec

:: String: defaults to "OPTIONS".

Information about a positional argument. Exposes the folowing fields.

posName

:: String: defaults to "".

posDoc

:: String: defaults to "".

posSec

:: String: defautts to "ARGUMENTS".

Initialize an OptInfo by providing a list of names. The fields optName, optDoc, and optSec can then be manipulated post-mortem, as in

inf =(optInfo    [ "i", "insufflation" ])
    { optName = "INSUFFERABLE"
    , optDoc  = "in the haunted house's harrow"
    , optSec  = "NOT FOR AUGHT"
    }

Names of one character in length will be prefixed by - on the command line, while longer names will be prefixed by --.

It is considered a programming error to provide an empty list of names to optInfo.

Initialize a PosInfo. The fields posName, posDoc, and posSec can then be manipulated post-mortem, as in

inf = posInfo
    { posName = "DEST"
    , posDoc  = "A destination for the operation."
    , posSec  = "DESTINATIONS"
    }

The fields posName and posDoc must be non-empty strings for the argument to be listed with its documentation under the section posSec of generated help.

Create a command line flag that can appear at most once on the command line. Yields False in absence and True in presence.

As flag but may appear an infinity of times. Yields a list of Trues as long as the number of times present.

vFlag v [ ( v1, ai1 ), ... ] is an argument that can be present at most once on the command line. It takes on the value vn when appearing as ain.

vFlagAll vs assoc is as vFlag except that it can be present an infinity of times. In absence, vs is yielded. When present, each value is collected in the order they appear.

opt v ai is an optional argument that yields v in absence, or an assigned value in presence. If the option is present, but no value is assigned, it is considered a user-error and usage is printed on exit.

defaultOpt def v ai is as opt except if it is present and no value is assigned on the command line, def is the result.

optAll vs ai is like opt except that it yields vs in absence and can appear an infinity of times. The values it is assigned on the command line are accumulated in the order they appear.

defaultOptAll def vs ai is like optAll except that if it is present without being assigned a value, the value def takes its place in the list of results.

pos n v ai is an argument defined by the nth positional argument on the command line. If absent the value v is returned.

revPos n v ai is as pos but counting from the end of the command line to the front.

posAny vs ai yields a list of all positional arguments or vs if none are present.

posLeft n vs ai yield a list of all positional arguments to the left of the nth positional argument or vs if there are none.

posRight n vs ai is as posLeft except yielding all values to the right of the nth positional argument.

revPosLeft n vs ai is as posLeft except n counts from the end of the command line to the front.

revPosRight n vs ai is as posRight except n counts from the end of the command line to the front.

value arg makes arg into a Term.

required arg converts arg into a Term such that it fails in the Nothing and yields a in the Just.

This is used for required positional arguments. There is nothing stopping you from using it with optional arguments, except that they would no longer be optional and it would be confusing from a user's perspective.

nonEmpty arg is a Term that fails if its result is empty. Intended for non-empty lists of positional arguments.

lastOf arg is a Term that fails if its result is empty and evaluates to the last element of the resulting list otherwise. Intended for lists of flags or options where the last takes precedence.