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    1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2017-2025, VU University Amsterdam
    7                              CWI Amsterdam
    8                              SWI-Prolog Solutions b.v.
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module(editline,
   38          [ el_wrap/0,                          % wrap user_input, etc.
   39            el_wrap/1,                          % +Options
   40            el_wrap/4,                          % +Prog, +Input, +Output, +Error
   41            el_wrap/5,                          % +Prog, +Input, +Output, +Error, +Options
   42            el_wrapped/1,                       % +Input
   43            el_unwrap/1,                        % +Input
   44
   45            el_source/2,                        % +Input, +File
   46            el_bind/2,                          % +Input, +Args
   47            el_set/2,                           % +Input, +Action
   48            el_get/2,                           % +Input, ?Property
   49            el_addfn/4,                         % +Input, +Name, +Help, :Goal
   50            el_cursor/2,                        % +Input, +Move
   51            el_line/2,                          % +Input, -Line
   52            el_insertstr/2,                     % +Input, +Text
   53            el_deletestr/2,                     % +Input, +Count
   54
   55            el_history/2,                       % +Input, ?Action
   56            el_history_events/2,                % +Input, -Events
   57            el_add_history/2,                   % +Input, +Line
   58            el_write_history/2,                 % +Input, +FileName
   59            el_read_history/2,                  % +Input, +FileName
   60
   61	    el_version/1			% -Version:integer
   62          ]).   63:- autoload(library(apply),[maplist/2,maplist/3]).   64:- autoload(library(lists),[reverse/2,max_list/2,append/3,member/2]).   65:- autoload(library(solution_sequences),[call_nth/2]).   66:- autoload(library(option), [merge_options/3]).   67
   68:- use_foreign_library(foreign(libedit4pl)).   69
   70:- initialization el_wrap_if_ok.   71
   72:- meta_predicate
   73    el_addfn(+,+,+,3).   74
   75:- multifile
   76    el_setup/1,                         % +Input
   77    el_wcwidth/2,                       % +Code, -Columns
   78    prolog:complete_input/4.

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.

   89el_wrap_if_ok :-
   90    \+ current_prolog_flag(readline, readline),
   91    stream_property(user_input, tty(true)),
   92    !,
   93    el_wrap.
   94el_wrap_if_ok.
 el_wrap is det
 el_wrap(+Options) 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).

Options processed:

pipes(+Boolean)
Used by Epilog windows to indicate we are reading from a Windows named pipe in overlapped mode. Ignored on other platforms.
history(+Size)
Size of the history. Default is defined by the Prolog flag history or 100 if this flag is not defined.
alert_signo(+Integer)
Signal used for making thread_signal/2 work while the thread is in a blocking system call.
  120el_wrap :-
  121    el_wrap([]).
  122
  123el_wrap(_) :-
  124    el_wrapped(user_input),
  125    !.
  126el_wrap(Options) :-
  127    stream_property(user_input, tty(true)), !,
  128    findall(Opt, el_default(Opt), Defaults),
  129    merge_options(Options, Defaults, Options1),
  130    el_wrap(swipl, user_input, user_output, user_error, Options1),
  131    add_prolog_commands(user_input),
  132    ignore(el_set(user_input, wordchars("_"))),
  133    forall(el_setup(user_input), true),
  134    enable_bracketed_paste(user_input),
  135    enable_word_motion(user_input),
  136    enable_windows_eof(user_input).
  137el_wrap(_).
  138
  139el_default(history(Size)) :-
  140    current_prolog_flag(history, Value),
  141    (   integer(Value),
  142        Value >= 0
  143    ->  Size = Value
  144    ;   Value == false
  145    ->  Size = 0
  146    ).
  147:- if(current_predicate(prolog_alert_signal/2)).  148el_default(alert_signo(SigNo)) :-
  149    prolog_alert_signal(SigName, SigName),
  150    current_signal(SigName, SigNo, _Handler).
  151:- endif.  152
  153add_prolog_commands(Input) :-
  154    el_addfn(Input, complete, 'Complete atoms and files', complete),
  155    el_addfn(Input, show_completions, 'List completions', show_completions),
  156    el_addfn(Input, electric, 'Indicate matching bracket', electric),
  157    el_addfn(Input, isearch_history, 'Incremental search in history',
  158             isearch_history),
  159    el_addfn(Input, bracketed_paste, 'Handle bracketed paste', bracketed_paste),
  160    el_bind(Input, ["^I",  complete]),
  161    el_bind(Input, ["^[?", show_completions]),
  162    el_bind(Input, ["^R",  isearch_history]),
  163    bind_electric(Input),
  164    add_paste_quoted(Input),
  165    el_source(Input, _).
 enable_bracketed_paste(+Input) is det
Sync bracketed paste mode with the current editor: bind ESC[200~ to bracketed_paste/3 and enable the mode in emacs, unbind and disable it in vi. In vi mode ESC leaves insert mode, so the ESC[200~ start marker cannot be dispatched as a key binding. Called from el_wrap/1 after the el_setup/1 hook, since that hook may switch editor with el_bind/2 -v or -e.
  176enable_bracketed_paste(Input) :-
  177    (   el_get(Input, editor(vi))
  178    ->  el_bind(Input, ['-r', "\e[200~"]),
  179        el_set(Input, bracketed_paste(false))
  180    ;   el_bind(Input, ["\e[200~", bracketed_paste]),
  181        el_set(Input, bracketed_paste(true))
  182    ).
 enable_word_motion(+Input) is det
Bind the xterm Ctrl+Left/Ctrl+Right escape sequences to word motion. The Epilog terminal sends ESC[1;5D and ESC[1;5C for these key combinations (see packages/xpce/src/txt/terminal.c); most xterm-compatible terminals use the same sequences. In vi mode the binding is installed in both the insert keymap and the command (alternative) keymap. Called after the el_setup/1 hooks since those may switch editor.

This complements the readline emulation, which already binds these sequences in its initialisation.

  197enable_word_motion(Input) :-
  198    el_bind(Input, ["\e[1;5D", 'ed-prev-word']),
  199    el_bind(Input, ["\e[1;5C", 'em-next-word']),
  200    (   el_get(Input, editor(vi))
  201    ->  el_bind(Input, ['-a', "\e[1;5D", 'vi-prev-word']),
  202        el_bind(Input, ['-a', "\e[1;5C", 'vi-next-word'])
  203    ;   true
  204    ).
 enable_windows_eof(+Input) is det
Bind ^Z to send end-of-file on Windows, matching the platform convention (compare with ^D on Unix). Routed through libedit's built-in em-delete-or-list (emacs) or vi-list-or-eof (vi), both of which return EOF on an empty line.
  213enable_windows_eof(Input) :-
  214    current_prolog_flag(windows, true),
  215    !,
  216    (   el_get(Input, editor(vi))
  217    ->  el_bind(Input, ["^Z", 'vi-list-or-eof'])
  218    ;   el_bind(Input, ["^Z", 'em-delete-or-list'])
  219    ).
  220enable_windows_eof(_).
 el_wrap(+ProgName:atom, +In:stream, +Out:stream, +Error:stream) is det
 el_wrap(+ProgName:atom, +In:stream, +Out:stream, +Error:stream, +Options) is det
Enable editline on the stream-triple <In,Out,Error>. From this moment on In is a handle to the command line editor. Options:
pipes(true)
Windows only. Assume the I/O is using pipes rather than a console. This is used for the Epilog terminal.
Arguments:
ProgName- is the name of the invoking program, used when reading the editrc(5) file to determine which settings to use.
  235el_wrap(ProgName, In, Out, Error) :-
  236    el_wrap(ProgName, In, Out, Error, []).
 el_setup(+In:stream) is nondet
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_set(+Input:stream, +Action) is semidet
Interface to el_set() and el_wset(). Currently provided values for Action are:
wordchars(+Text)
Set the characters considered part of a word. This feature depends on el_wsey() EL_WORDCHARS, which is only provided in some recent versions of libedit.
bracketed_paste(+Boolean)
Enable or disable bracketed paste mode. When enabled, the terminal is asked to bracket pasted text with ESC[200~ / ESC[201~ before each prompt, which the default bindings route through bracketed_paste/3. Disabling sends the matching ESC[?2004l sequence immediately. enable_bracketed_paste/1 manages this based on the current editor; you normally do not need to set it directly.

This predicate fails silently of Action is not implemented. Illegal input raises in an exception.

 el_get(+Input:stream, ?Property) is semidet
Interface to el_get(). Currently supported Property terms:
editor(-Editor)
Editor is unified with emacs or vi, reflecting the current keymap selected via el_bind/2 with -e / -v.
bracketed_paste(-Boolean)
Whether bracketed paste mode is currently enabled; see el_set/2.

Any other Property raises a domain_error(editline_property, _).

 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.
getsize(-Integer)
Unify Integer with the maximum size of the history. Note that this is not the same as el_history() using H_GETSIZE, which returns the number of currently saved events. The number of saved events may be computed from first and last or using el_history_events/2.
setunique(+Boolean)
Set flag that adjacent identical event strings should not be entered into the history.
first(-Num, -String)
last(-Num, -String)
curr(-Num, -String)
prev(-Num, -String)
next(-Num, -String)
Retrieve an event. Num is the event number and String is the event string. Note that first is the most recent event and last the oldest.
set(Num)
Set the notion of current to Num.
prev_str(+Search, -Num, -String)
next_str(+Search, -Num, -String)
Retrieve the previous or next event whose String starts with Search.
event(+Num, -String)
True when String represents event Num. This is an extension to the history() API, retrieving a numbered event without changing the current notion.
 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.
 el_version(-Version)
True when Version is LIBEDIT_MAJOR*10000 + LIBEDIT_MINOR*100. The version is generated from the include file histedit.h, which implies that the actual version of the shared library may be different.
 prolog:history(+Input, ?Action) is semidet
Provide the plugable interface into the system command line management.
  435:- multifile
  436    prolog:history/2.  437
  438prolog:history(Input, enabled) :-
  439    !,
  440    el_wrapped(Input),
  441    el_history(Input, getsize(Size)),
  442    Size > 0.
  443prolog:history(Input, add(Line)) :-
  444    !,
  445    el_add_history(Input, Line).
  446prolog:history(Input, load(File)) :-
  447    !,
  448    compat_read_history(Input, File).
  449prolog:history(Input, save(File)) :-
  450    !,
  451    el_write_history(Input, File).
  452prolog:history(Input, events(Events)) :-
  453    !,
  454    el_history_events(Input, Events).
  455prolog:history(Input, Command) :-
  456    public_command(Command),
  457    !,
  458    el_history(Input, Command).
  459
  460public_command(first(_Num, _String)).
  461public_command(curr(_Num, _String)).
  462public_command(event(_Num, _String)).
  463public_command(prev_str(_Search, _Num, _String)).
  464public_command(clear).
 compat_read_history(+Input, +File) is det
Read the saved history. This loads both the LibEdit and old history format used by swipl-win.exe before migrating to SDL.
  471compat_read_history(Input, File) :-
  472    catch(el_read_history(Input, File), error(editline(_),_), fail),
  473    !.
  474compat_read_history(Input, File) :-
  475    access_file(File, read),
  476    setup_call_cleanup(
  477        open(File, read, In, [encoding(utf8)]),
  478        read_old_history(Input, In),
  479        close(In)),
  480    !.
  481compat_read_history(_, _).
  482
  483read_old_history(Input, From) :-
  484    catch('$raw_read'(From, Line), error(_,_), fail),
  485    (   Line == end_of_file
  486    ->  true
  487    ;   string_concat(Line, '.', Event),
  488        el_add_history(Input, Event),
  489        read_old_history(Input, From)
  490    ).
  491
  492		 /*******************************
  493		 *        ELECTRIC CARET	*
  494		 *******************************/
 bind_electric(+Input) is det
Bind known close statements for electric input
  500bind_electric(Input) :-
  501    forall(bracket(_Open, Close), bind_code(Input, Close, electric)),
  502    forall(quote(Close), bind_code(Input, Close, electric)).
  503
  504bind_code(Input, Code, Command) :-
  505    string_codes(Key, [Code]),
  506    el_bind(Input, [Key, Command]).
 electric(+Input, +Char, -Continue) is det
  511electric(Input, Char, Continue) :-
  512    string_codes(Str, [Char]),
  513    el_insertstr(Input, Str),
  514    el_line(Input, line(Before, _)),
  515    (   string_codes(Before, Codes),
  516        nesting(Codes, 0, Nesting),
  517        reverse(Nesting, [Close|RevNesting])
  518    ->  (   Close = open(_,_)                   % open quote
  519        ->  Continue = refresh
  520        ;   matching_open(RevNesting, Close, _, Index)
  521        ->  string_length(Before, Len),         % Proper match
  522            Move is Index-Len,
  523            Continue = electric(Move, 500, refresh)
  524        ;   Continue = refresh_beep             % Not properly nested
  525        )
  526    ;   Continue = refresh_beep
  527    ).
  528
  529matching_open_index(String, Index) :-
  530    string_codes(String, Codes),
  531    nesting(Codes, 0, Nesting),
  532    reverse(Nesting, [Close|RevNesting]),
  533    matching_open(RevNesting, Close, _, Index).
  534
  535matching_open([Open|Rest], Close, Rest, Index) :-
  536    Open = open(Index,_),
  537    match(Open, Close),
  538    !.
  539matching_open([Close1|Rest1], Close, Rest, Index) :-
  540    Close1 = close(_,_),
  541    matching_open(Rest1, Close1, Rest2, _),
  542    matching_open(Rest2, Close, Rest, Index).
  543
  544match(open(_,Open),close(_,Close)) :-
  545    (   bracket(Open, Close)
  546    ->  true
  547    ;   Open == Close,
  548        quote(Open)
  549    ).
  550
  551bracket(0'(, 0')).
  552bracket(0'[, 0']).
  553bracket(0'{, 0'}).
  554
  555quote(0'\').
  556quote(0'\").
  557quote(0'\`).
  558
  559nesting([], _, []).
  560nesting([H|T], I, Nesting) :-
  561    (   bracket(H, _Close)
  562    ->  Nesting = [open(I,H)|Nest]
  563    ;   bracket(_Open, H)
  564    ->  Nesting = [close(I,H)|Nest]
  565    ),
  566    !,
  567    I2 is I+1,
  568    nesting(T, I2, Nest).
  569nesting([0'0, 0'\'|T], I, Nesting) :-
  570    !,
  571    phrase(skip_code, T, T1),
  572    difflist_length(T, T1, Len),
  573    I2 is I+Len+2,
  574    nesting(T1, I2, Nesting).
  575nesting([H|T], I, Nesting) :-
  576    quote(H),
  577    !,
  578    (   phrase(skip_quoted(H), T, T1)
  579    ->  difflist_length(T, T1, Len),
  580        I2 is I+Len+1,
  581        Nesting = [open(I,H),close(I2,H)|Nest],
  582        nesting(T1, I2, Nest)
  583    ;   Nesting = [open(I,H)]                   % Open quote
  584    ).
  585nesting([_|T], I, Nesting) :-
  586    I2 is I+1,
  587    nesting(T, I2, Nesting).
  588
  589difflist_length(List, Tail, Len) :-
  590    difflist_length(List, Tail, 0, Len).
  591
  592difflist_length(List, Tail, Len0, Len) :-
  593    List == Tail,
  594    !,
  595    Len = Len0.
  596difflist_length([_|List], Tail, Len0, Len) :-
  597    Len1 is Len0+1,
  598    difflist_length(List, Tail, Len1, Len).
  599
  600skip_quoted(H) -->
  601    [H],
  602    !.
  603skip_quoted(H) -->
  604    "\\", [H],
  605    !,
  606    skip_quoted(H).
  607skip_quoted(H) -->
  608    [_],
  609    skip_quoted(H).
  610
  611skip_code -->
  612    "\\", [_],
  613    !.
  614skip_code -->
  615    [_].
  616
  617
  618		 /*******************************
  619		 *           COMPLETION		*
  620		 *******************************/
 complete(+Input, +Char, -Continue) is det
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.
  631:- dynamic
  632    last_complete/2.  633
  634complete(Input, _Char, Continue) :-
  635    el_line(Input, line(Before, After)),
  636    ensure_input_completion,
  637    prolog:complete_input(Before, After, Delete, Completions),
  638    (   Completions = [One]
  639    ->  string_length(Delete, Len),
  640        el_deletestr(Input, Len),
  641        complete_text(One, Text),
  642        el_insertstr(Input, Text),
  643        Continue = refresh
  644    ;   Completions == []
  645    ->  Continue = refresh_beep
  646    ;   get_time(Now),
  647        retract(last_complete(TLast, Before)),
  648        Now - TLast < 2
  649    ->  nl(user_error),
  650        list_alternatives(Completions),
  651        Continue = redisplay
  652    ;   retractall(last_complete(_,_)),
  653        get_time(Now),
  654        asserta(last_complete(Now, Before)),
  655        common_competion(Completions, Extend),
  656        (   Delete == Extend
  657        ->  Continue = refresh_beep
  658        ;   string_length(Delete, Len),
  659            el_deletestr(Input, Len),
  660            el_insertstr(Input, Extend),
  661            Continue = refresh
  662        )
  663    ).
  664
  665:- dynamic
  666    input_completion_loaded/0.  667
  668ensure_input_completion :-
  669    input_completion_loaded,
  670    !.
  671ensure_input_completion :-
  672    predicate_property(prolog:complete_input(_,_,_,_),
  673                       number_of_clauses(N)),
  674    N > 0,
  675    !.
  676ensure_input_completion :-
  677    exists_source(library(console_input)),
  678    !,
  679    use_module(library(console_input), []),
  680    asserta(input_completion_loaded).
  681ensure_input_completion.
 show_completions(+Input, +Char, -Continue) is det
Editline command to show possible completions.
  688show_completions(Input, _Char, Continue) :-
  689    el_line(Input, line(Before, After)),
  690    prolog:complete_input(Before, After, _Delete, Completions),
  691    nl(user_error),
  692    list_alternatives(Completions),
  693    Continue = redisplay.
  694
  695complete_text(Text-_Comment, Text) :- !.
  696complete_text(Text, Text).
 common_competion(+Alternatives, -Common) is det
True when Common is the common prefix of all candidate Alternatives.
  702common_competion(Alternatives, Common) :-
  703    maplist(atomic, Alternatives),
  704    !,
  705    common_prefix(Alternatives, Common).
  706common_competion(Alternatives, Common) :-
  707    maplist(complete_text, Alternatives, AltText),
  708    !,
  709    common_prefix(AltText, Common).
 common_prefix(+Atoms, -Common) is det
True when Common is the common prefix of all Atoms.
  715common_prefix([A1|T], Common) :-
  716    common_prefix_(T, A1, Common).
  717
  718common_prefix_([], Common, Common).
  719common_prefix_([H|T], Common0, Common) :-
  720    common_prefix(H, Common0, Common1),
  721    common_prefix_(T, Common1, Common).
 common_prefix(+A1, +A2, -Prefix:string) is det
True when Prefix is the common prefix of the atoms A1 and A2
  727common_prefix(A1, A2, Prefix) :-
  728    sub_atom(A1, 0, _, _, A2),
  729    !,
  730    Prefix = A2.
  731common_prefix(A1, A2, Prefix) :-
  732    sub_atom(A2, 0, _, _, A1),
  733    !,
  734    Prefix = A1.
  735common_prefix(A1, A2, Prefix) :-
  736    atom_codes(A1, C1),
  737    atom_codes(A2, C2),
  738    list_common_prefix(C1, C2, C),
  739    string_codes(Prefix, C).
  740
  741list_common_prefix([H|T0], [H|T1], [H|T]) :-
  742    !,
  743    list_common_prefix(T0, T1, T).
  744list_common_prefix(_, _, []).
 list_alternatives(+Alternatives)
List possible completions at the current point.
To be done
- currently ignores the Comment in Text-Comment alternatives.
  754list_alternatives(Alternatives) :-
  755    maplist(atomic, Alternatives),
  756    !,
  757    length(Alternatives, Count),
  758    maplist(atom_length, Alternatives, Lengths),
  759    max_list(Lengths, Max),
  760    tty_size(_, Cols),
  761    ColW is Max+2,
  762    Columns is max(1, Cols // ColW),
  763    RowCount is (Count+Columns-1)//Columns,
  764    length(Rows, RowCount),
  765    to_matrix(Alternatives, Rows, Rows),
  766    (   RowCount > 11
  767    ->  length(First, 10),
  768        Skipped is RowCount - 10,
  769        append(First, _, Rows),
  770        maplist(write_row(ColW), First),
  771        format(user_error, '... skipped ~D rows~n', [Skipped])
  772    ;   maplist(write_row(ColW), Rows)
  773    ).
  774list_alternatives(Alternatives) :-
  775    maplist(complete_text, Alternatives, AltText),
  776    list_alternatives(AltText).
  777
  778to_matrix([], _, Rows) :-
  779    !,
  780    maplist(close_list, Rows).
  781to_matrix([H|T], [RH|RT], Rows) :-
  782    !,
  783    add_list(RH, H),
  784    to_matrix(T, RT, Rows).
  785to_matrix(List, [], Rows) :-
  786    to_matrix(List, Rows, Rows).
  787
  788add_list(Var, Elem) :-
  789    var(Var), !,
  790    Var = [Elem|_].
  791add_list([_|T], Elem) :-
  792    add_list(T, Elem).
  793
  794close_list(List) :-
  795    append(List, [], _),
  796    !.
  797
  798write_row(ColW, Row) :-
  799    length(Row, Columns),
  800    make_format(Columns, ColW, Format),
  801    format(user_error, Format, Row).
  802
  803make_format(N, ColW, Format) :-
  804    format(string(PerCol), '~~w~~t~~~d+', [ColW]),
  805    Front is N - 1,
  806    length(LF, Front),
  807    maplist(=(PerCol), LF),
  808    append(LF, ['~w~n'], Parts),
  809    atomics_to_string(Parts, Format).
  810
  811
  812		 /*******************************
  813		 *             SEARCH		*
  814		 *******************************/
 isearch_history(+Input, +Char, -Continue) is det
Incremental search through the history. The behavior is based on GNU readline.
  821isearch_history(Input, _Char, Continue) :-
  822    el_line(Input, line(Before, After)),
  823    string_concat(Before, After, Current),
  824    string_length(Current, Len),
  825    search_print('', "", Current),
  826    search(Input, "", Current, 1, Line),
  827    el_deletestr(Input, Len),
  828    el_insertstr(Input, Line),
  829    Continue = redisplay.
  830
  831search(Input, For, Current, Nth, Line) :-
  832    el_getc(Input, Next),
  833    Next \== -1,
  834    !,
  835    search(Next, Input, For, Current, Nth, Line).
  836search(_Input, _For, _Current, _Nth, "").
  837
  838search(7, _Input, _, Current, _, Current) :-    % C-g: abort
  839    !,
  840    clear_line.
  841search(18, Input, For, Current, Nth, Line) :-   % C-r: search previous
  842    !,
  843    N2 is Nth+1,
  844    search_(Input, For, Current, N2, Line).
  845search(19, Input, For, Current, Nth, Line) :-   % C-s: search next
  846    !,
  847    N2 is max(1,Nth-1),
  848    search_(Input, For, Current, N2, Line).
  849search(127, Input, For, Current, _Nth, Line) :- % DEL/BS: shorten search
  850    sub_string(For, 0, _, 1, For1),
  851    !,
  852    search_(Input, For1, Current, 1, Line).
  853search(Char, Input, For, Current, Nth, Line) :-
  854    code_type(Char, cntrl),
  855    !,
  856    search_end(Input, For, Current, Nth, Line),
  857    el_push(Input, Char).
  858search(Char, Input, For, Current, _Nth, Line) :-
  859    format(string(For1), '~w~c', [For,Char]),
  860    search_(Input, For1, Current, 1, Line).
  861
  862search_(Input, For1, Current, Nth, Line) :-
  863    (   find_in_history(Input, For1, Current, Nth, Candidate)
  864    ->  search_print('', For1, Candidate)
  865    ;   search_print('failed ', For1, Current)
  866    ),
  867    search(Input, For1, Current, Nth, Line).
  868
  869search_end(Input, For, Current, Nth, Line) :-
  870    (   find_in_history(Input, For, Current, Nth, Line)
  871    ->  true
  872    ;   Line = Current
  873    ),
  874    clear_line.
  875
  876find_in_history(_, "", Current, _, Current) :-
  877    !.
  878find_in_history(Input, For, _, Nth, Line) :-
  879    el_history_events(Input, History),
  880    call_nth(( member(_N-Line, History),
  881               sub_string(Line, _, _, _, For)
  882             ),
  883             Nth),
  884    !.
  885
  886search_print(State, Search, Current) :-
  887    format(user_error, '\r(~wreverse-i-search)`~w\': ~w\e[0K',
  888           [State, Search, Current]).
  889
  890clear_line :-
  891    format(user_error, '\r\e[0K', []).
  892
  893
  894                /*******************************
  895                *         PASTE QUOTED         *
  896                *******************************/
  897
  898:- meta_predicate
  899    with_quote_flags(+,+,0).  900
  901add_paste_quoted(Input) :-
  902    current_prolog_flag(gui, true),
  903    !,
  904    el_addfn(Input, paste_quoted, 'Paste as quoted atom', paste_quoted),
  905    el_bind(Input, ["^Y",  paste_quoted]).
  906add_paste_quoted(_).
 paste_quoted(+Input, +Char, -Continue) is det
Paste the selection as quoted Prolog value. The quoting type depends on the quote before the caret. If there is no quote before the caret we paste as an atom.
  914paste_quoted(Input, _Char, Continue) :-
  915    clipboard_content(String),
  916    quote_text(Input, String, Quoted),
  917    el_insertstr(Input, Quoted),
  918    Continue = refresh.
  919
  920quote_text(Input, String, Value) :-
  921    el_line(Input, line(Before, _After)),
  922    (   sub_string(Before, _, 1, 0, Quote)
  923    ->  true
  924    ;   Quote = "'"
  925    ),
  926    quote_text(Input, Quote, String, Value).
  927
  928quote_text(Input, "'", Text, Quoted) =>
  929    format(string(Quoted), '~q', [Text]),
  930    el_deletestr(Input, 1).
  931quote_text(Input, "\"", Text, Quoted) =>
  932    atom_string(Text, String),
  933    with_quote_flags(
  934        string, codes,
  935        format(string(Quoted), '~q', [String])),
  936    el_deletestr(Input, 1).
  937quote_text(Input, "`", Text, Quoted) =>
  938    atom_string(Text, String),
  939    with_quote_flags(
  940        codes, string,
  941        format(string(Quoted), '~q', [String])),
  942    el_deletestr(Input, 1).
  943quote_text(_, _, Text, Quoted) =>
  944    format(string(Quoted), '~q', [Text]).
  945
  946with_quote_flags(Double, Back, Goal) :-
  947    setup_call_cleanup(
  948        ( push_prolog_flag(double_quotes, Double),
  949          push_prolog_flag(back_quotes, Back) ),
  950        Goal,
  951        ( pop_prolog_flag(back_quotes),
  952          pop_prolog_flag(double_quotes) )).
  953
  954clipboard_content(Text) :-
  955    current_prolog_flag(gui, true),
  956    !,
  957    autoload_call(in_pce_thread_sync(
  958                      autoload_call(
  959                          get(@(display), paste, primary, string(Text))))).
  960clipboard_content("").
  961
  962
  963                /*******************************
  964                *       BRACKETED PASTE        *
  965                *******************************/
 bracketed_paste(+Input, +Char, -Continue) is det
Handler for the bracketed paste start sequence ESC[200~. Reads characters until the end sequence ESC[201~ is received and inserts the collected text literally, bypassing per-character key dispatch.

The terminal is asked to enable bracketed paste mode (ESC[?2004h) from the C layer each time a prompt is issued.

  976bracketed_paste(Input, _Char, Continue) :-
  977    collect_paste(Input, [], RevCodes),
  978    reverse(RevCodes, Codes),
  979    string_codes(Text, Codes),
  980    el_insertstr(Input, Text),
  981    Continue = refresh.
 collect_paste(+Input, +RevAcc, -RevResult) is det
Read characters one at a time, accumulating them in reverse order. Stop when the reversed accumulator starts with the end sequence ESC[201~ (27,91,50,48,49,126) and return the reversed content that precedes it.
  990collect_paste(Input, RevCodes, Result) :-
  991    el_getc(Input, Char),
  992    (   Char == -1                          % EOF / error
  993    ->  Result = RevCodes
  994    ;   paste_char(Char, Char1),
  995        RevCodes1 = [Char1|RevCodes],
  996        (   RevCodes1 = [0'~,0'1,0'0,0'2,0'[,0'\e|Rest]  % ESC[201~ reversed
  997        ->  Result = Rest
  998        ;   collect_paste(Input, RevCodes1, Result)
  999        )
 1000    ).
 paste_char(+Raw, -Char) is det
Translate a raw character code from bracketed paste to the intended code. The tty line discipline in edit mode has INLCR set, which maps LF (10) to CR (13) before libedit reads it. We reverse that here so pasted newlines are inserted as actual newlines.
 1009paste_char(0'\r, 0'\n) :- !.               % CR → LF (INLCR maps \n to \r in edit mode)
 1010paste_char(C,   C).
 1011
 1012
 1013                /*******************************
 1014                *           MESSAGE            *
 1015                *******************************/
 1016
 1017:- multifile prolog:error_message//1. 1018
 1019prolog:error_message(editline(Msg)) -->
 1020    [ 'editline: ~s'-[Msg] ]