Io (beluga.Harpoon.Io)

exception Io_error of exn

type t

Type of IO capabilities. Includes:

prompting the user for input,
displaying a message to the user.

When a function needs user interactivity, pass this object to it. If it only needs an output capability, see Format.formatter.

val make : InputPrompt.t -> Stdlib.Format.formatter -> t

Constructs an IO capability.

val formatter : t -> Stdlib.Format.formatter

Extracts the formatter from an IO capability.

val prompt_number : t -> int

Gets the number of the last prompt that was shown.

val printf : t -> ('a, Stdlib.Format.formatter, unit) Stdlib.format -> 'a

Displays a formatted message.

val default_prompt_source : string

Default value used for the filename when displaying parse errors.

val read_line : 
  ?source:string ->
  t ->
  msg:string ->
  history_file:string option ->
  Beluga_syntax.Location.t * string

read_line ?source io ~msg ~history_file prompts the user for input by displaying the given message. The input line is output. The returned location is an empty location having source as filename and the number of lines input so far as the line number.

The default value of ?source is default_source_prompt.

An exception is raised if there are no more lines in the input.

val prompt_input : 
  ?source:string ->
  t ->
  msg:string ->
  history_file:string option ->
  (Beluga_syntax.Location.t -> string -> 'a) ->
  'a

prompt_input ?source io ~msg ~history_file f repeatedly prompts the user for an input to pass to f until a call to f does not throw. That is, it calls read_line ?source io ~msg ~history_file, then passes the result to f. If f raises an exception, then it is caught, printed, and prompt_input is called once more.

Make sure that f can fail gracefully (by cleaning up in case of a raised exception) because any exception from f will be suppressed.