editline.pl -- BSD libedit based command line editing

This library wraps the BSD libedit command line editor. The binding provides a high level API to enable command line editing on the Prolog user streams and low level predicates to apply the library on other streams and program the library.

el_wrap is det

Enable using editline on the standard user streams if user_input is connected to a terminal. This is the high level predicate used for most purposes. The remainder of the library interface deals with low level predicates that allows for applying and programming libedit in non-standard situations.

The library is registered with ProgName set to swipl (see el_wrap/4).

el_wrap(+ProgName:atom, +In:stream, +Out:stream, +Error:stream) is det

Enable editline on the stream-triple <In,Out,Error>. From this moment on In is a handle to the command line editor.

Arguments:

ProgName - is the name of the invoking program, used when reading the editrc(5) file to determine which settings to use.

el_setup(+In:stream) is nondet[multifile]

This hooks is called as forall(el_setup(Input), true) after the input stream has been wrapped, the default Prolog commands have been added and the default user setup file has been sourced using el_source/2. It can be used to define and bind additional commands.

el_wrapped(+In:stream) is semidet

True if In is a stream wrapped by el_wrap/3.

el_unwrap(+In:stream) is det

Remove the libedit wrapper for In and the related output and error streams.

bug: - The wrapper creates FILE* handles that cannot be closed and thus wrapping and unwrapping implies a (modest) memory leak.

el_source(+In:stream, +File) is det

Initialise editline by reading the contents of File. If File is unbound try $HOME/.editrc

el_bind(+In:stream, +Args) is det

Invoke the libedit bind command with the given arguments. The example below lists the current key bindings.

?- el_bind(user_input, ['-a']).

The predicate el_bind/2 is typically used to bind commands defined using el_addfn/4. Note that the C proxy function has only the last character of the command as context to find the Prolog binding. This implies we cannot both bind e.g., "^[?" *and "?" to a Prolog function.

See also: - editrc(5) for more information.

el_addfn(+Input:stream, +Command, +Help, :Goal) is det

Add a new command to the command line editor associated with Input. Command is the name of the command, Help is the help string printed with e.g. bind -a (see el_bind/2) and Goal is called of the associated key-binding is activated. Goal is called as

call(:Goal, +Input, +Char, -Continue)

where Input is the input stream providing access to the editor, Char the activating character and Continue must be instantated with one of the known continuation codes as defined by libedit: norm, newline, eof, arghack, refresh, refresh_beep, cursor, redisplay, error or fatal. In addition, the following Continue code is provided.

electric(Move, TimeOut, Continue): Show electric caret at Move positions to the left of the normal cursor positions for the given TimeOut. Continue as defined by the Continue value.

The registered Goal typically used el_line/2 to fetch the input line and el_cursor/2, el_insertstr/2 and/or el_deletestr/2 to manipulate the input line.

Normally el_bind/2 is used to associate the defined command with a keyboard sequence.

See also: - el_set(3) EL_ADDFN for details.

el_line(+Input:stream, -Line) is det

Fetch the currently buffered input line. Line is a term

line(Before,
After)

, where Before is a string holding the text before the cursor and After is a string holding the text after the cursor.

el_cursor(+Input:stream, +Move:integer) is det

Move the cursor Move character forwards (positive) or backwards (negative).

el_insertstr(+Input:stream, +Text) is det

Insert Text at the cursor.

el_deletestr(+Input:stream, +Count) is det

Delete Count characters before the cursor.

el_history(+In:stream, ?Action) is det

Perform a generic action on the history. This provides an incomplete interface to history() from libedit. Supported actions are:

clear: Clear the history.
setsize(+Integer): Set size of history to size elements.
setunique(+Boolean): Set flag that adjacent identical event strings should not be entered into the history.

el_history_events(+In:stream, -Events:list(pair)) is det

Unify Events with a list of pairs of the form Num-String, where Num is the event number and String is the associated string without terminating newline.

el_add_history(+In:stream, +Line:text) is det

Add a line to the command line history.

el_read_history(+In:stream, +File:file) is det

Read the history saved using el_write_history/2.

Arguments:

File

- is a file specification for absolute_file_name/3.

el_write_history(+In:stream, +File:file) is det

Save editline history to File. The history may be reloaded using el_read_history/2.

Arguments:

File

- is a file specification for absolute_file_name/3.

bind_electric(+Input) is det[private]

Bind known close statements for electric input

electric(+Input, +Char, -Continue) is det[private]

complete(+Input, +Char, -Continue) is det[private]

Implementation of the registered complete editline function. The predicate is called with three arguments, the first being the input stream used to access the libedit functions and the second the activating character. The last argument tells libedit what to do. Consult el_set(3), EL_ADDFN for details.

show_completions(+Input, +Char, -Continue) is det[private]

Editline command to show possible completions.

common_competion(+Alternatives, -Common) is det[private]

True when Common is the common prefix of all candidate Alternatives.

common_prefix(+Atoms, -Common) is det[private]

True when Common is the common prefix of all Atoms.

common_prefix(+A1, +A2, -Prefix:string) is det[private]

True when Prefix is the common prefix of the atoms A1 and A2

list_alternatives(+Alternatives)[private]

List possible completions at the current point.

To be done: - currently ignores the Comment in Text-Comment alternatives.

isearch_history(+Input, +Char, -Continue) is det[private]

Incremental search through the history. The behavior is based on GNU readline.