clip/arg

Functions for building Args. An Arg is a positional option.

Types

Arg

opaque </>

pub opaque type Arg(a)

Values

default

</>

pub fn default(arg: Arg(a), default: a) -> Arg(a)

Provide a default value for an Arg when it is not provided by the user.

float

</>

pub fn float(arg: Arg(String)) -> Arg(Float)

Modify an Arg(String) to produce a Float.

arg.new("height")
|> arg.float

Note: float changes the type of an Arg and therefore clears any previously set default value.

help

</>

pub fn help(arg: Arg(a), help: String) -> Arg(a)

Add help text to an Arg.

int

</>

pub fn int(arg: Arg(String)) -> Arg(Int)

Modify an Arg(String) to produce an Int.

arg.new("age")
|> arg.int

Note: int changes the type of an Arg and therefore clears any previously set default value.

map

</>

pub fn map(arg: Arg(a), f: fn(a) -> b) -> Arg(b)

Modify the value produced by an Arg in a way that cannot fail.

arg.new("name")
|> arg.map(fn(name) { string.uppercase(name) })

Note: map can change the type of an Arg and therefore clears any previously set default value.

new

</>

pub fn new(name: String) -> Arg(String)

Create a new Arg with the provided name. New Args always initially produce a String, which is the unmodified value given by the user on the command line.

optional

</>

pub fn optional(arg: Arg(a)) -> Arg(Result(a, Nil))

Transform an Arg(a) to an Arg(Result(a, Nil), making it optional.

try_map

</>

pub fn try_map(
  arg: Arg(a),
  f: fn(a) -> Result(b, String),
) -> Arg(b)

Modify the value produced by an Arg in a way that may fail.

arg.new("age")
|> arg.try_map(fn(age_str) {
  case int.parse(age_str) {
    Ok(age) -> Ok(age)
    Error(Nil) -> Error("Unable to parse integer")
  }
})

Note: try_map can change the type of an Arg and therefore clears any previously set default value.