option -package:turtle

option x p will either parse p or return x without consuming any input.

option x p tries to apply parser p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

priority  = option 0 (do{ d <- digit
; return (digitToInt d)
})

Builder for an option using the given reader. This is a regular option, and should always have either a long or short name specified in the modifiers (or both).

nameParser = option str ( long "name" <> short 'n' )

option x p tries to apply action p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

priority  = option 0 (digitToInt <$> digit)

Create an option taking a single OptDescr. No explicit Name is given for the Option, the name is the first LFlag given. Example: option sf lf d get set * sf: Short option name, for example: ['d']. No hyphen permitted. * lf: Long option name, for example: ["debug"]. No hyphens permitted. * d: Description of the option, shown to the user in help messages. * get: Get the current value of the flag. * set: Set the value of the flag. Gets the current value of the flag as a parameter.

Combinator for the <option> element. Example:

option $ span $ toHtml "foo"

Result:

<option><span>foo</span></option>

option x p tries to apply parser p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

priority  = option 0 (do{ d <- digit
; return (digitToInt d)
})

option x p tries to apply the parser p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

option x p = p <|> pure x

See also: optional.

option x p tries to apply parser p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

priority = option 0 (digitToInt <$> digit)

option x p will either parse p or return x without consuming any input.

option def p will try to parse p and, if it fails, simply return def without consuming any input.

option x p will either parse p or return x without consuming any input.

option x p will either parse p or return x without consuming any input.

Try to parse an argument. You'll also need to add a reader, at least one long or short, and a metavar. Multiple options are redundant.

option x p tries to apply parser p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

Apply a list of options to a plot resolving any pending options.

Parse something if you can, else return first value

option a p = p // unit a