: [[image:iciclesimage]]

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== Ido and IswitchB ==

Libraries [[Ido]] and IswitchB are alternatives to '''Icicles''' that also
enhance [[minibuffer]] [[completion]] in various ways.  Their UIs are
similar to each other -- Ido essentially extends %%IswitchB%%'s
buffer-name completion to file names as well.  Neither completes
other kinds of candidates.  They work only for [[buffer]] names or
file names, but you can advise the standard completion functions
to get them to use Ido completion more generally.

The behavior of Ido and %%IswitchB%% is different from the default
'''Icicles''' behavior.  If you prefer their behavior for buffers then
you can just use %%IswitchB%%  and '''Icicles''' together.  You cannot use
'''Icicles''' and Ido together, however -- they use the minibuffer in
incompatible ways.

The default behavior of '''Icicles''' is different, but you can make
'''Icicles''' behave more like Ido if you like.  It would be a mistake
to look for a complete reproduction of the Ido behavior in
'''Icicles''', however.  If you want exactly the same behavior as Ido,
then use Ido. ;-)

The '''Icicles''' UI is different by design.  Some of
this difference in approach has to do with the fact that Ido is
specialized to buffer- and file-name completion.  The generality
of '''Icicles''' makes a different approach appropriate.  '''Icicles''' has many additional features that are not available in
other libraries, but its main advantage is its
generality: you use the same user interface for input of any kind. (See [[KillingBuffers#UsingIcicles|KillingBuffers]] for an illustration of this generality, as well as some musings on special vs general solutions.)  As you learn
more about '''Icicles''' you may begin to appreciate its approach, even
if you are a diehard Ido addict.

This section summarizes some differences between '''Icicles''' and Ido
and tells you how you can get more Ido-like behavior in '''Icicles''' if
that's what you prefer.  It does not cover '''Icicles''' features that have no counterpart in Ido or features that they have
in common (except to emphasize some differences).

If you have the Ido habit but want to give '''Icicles''' a try, then
this section is for you.  I recommend, however, that you give the
default '''Icicles''' behavior a good try before convincing yourself
that you still prefer a more Ido-like approach.

See also the references at the section end for other sections that
go into more detail about some of the things mentioned here.

==== 1. Incremental completion ==== 

By default, '''Icicles''' does not turn on
   [[incremental completion]] until you have hit `TAB' or `S-TAB' to
   display the matching candidates.  Ido turns it on immediately.
   You can get that behavior by setting [[option]]
   '''`<tt>[[Icicles - Customization and General Tips#icicle-show-Completions-initially-flag|icicle-show-Completions-initially-flag]]</tt>'''' to `t'.

You can get an intermediate behavior in this regard by instead
   setting option '''`<tt>[[Icicles - Customization and General Tips#icicle-incremental-completion|icicle-incremental-completion]]</tt>'''' to a value that is neither `nil' nor `t'.  That makes '''Icicles''' show the matching candidates as soon as you start typing input, but not before that.  See also [[Icicles - Icompletion]] and option '''`<tt>[[Icicles - Customization and General Tips#icicle-incremental-completion-delay|icicle-incremental-completion-delay]]</tt>''''.





==== 2. Non-expansion of minibuffer input ====

By default, '''Icicles''' expands your [[minibuffer]] input when you complete.  This is like vanilla Emacs (for prefix completion), but it is unlike Ido, which only shows you the available candidates but does not change your input text.  You can get this non-expansion behavior in '''Icicles''' by setting option '''`<tt>[[Icicles - Customization and General Tips#icicle-expand-input-to-common-match|icicle-expand-input-to-common-match]]</tt>'''' to '''##0##'''.
See [[Icicles - Icompletion#InputExpansion|Incremental Completion (Input Expansion) in the Minibuffer]].








==== 3. Matching ====

By default, Ido uses substring matching for
   completion.  You can hit a key to switch to [[prefix completion|prefix matching]],
   "flex" matching, or [[apropos completion|regexp matching]].  '''Icicles''' gives you these
   same matching possibilities, and more.  (What Ido calls "flex
   matching" '''Icicles''' calls "[[scatter matching]]".)  The main
   difference here is that '''Icicles''' [[regexp]] support is general and
   complete.  Regexp-matching in Ido does not work with Ido-style
   completion.



==== 4. Current candidate, cycling, sorting ====

Both Ido and '''Icicles'''
   have a notion of "'''current candidate'''".  In Ido, completion
   candidates are presented in a predefined sort order, most
   recently used first.  The current candidate is the first one.
   You cycle candidates by moving the first to last or the last to
   first.

In '''Icicles''', you can switch among any number of sort orders at
   any time by hitting a key.  (And you can easily define your own
   sort orders.)  When you [[Icicles - Cycling Completions|cycle]]  candidates, the candidates stay
   in order.  If the candidates are displayed in `*Completions*'
   then the current one is highlighted there, in place.  The
   highlight moves, not the candidate.


==== 5. Input editing ====

In Ido, cycling does not replace your input by
   the current candidate.  To edit the current candidate you hit a
   key to enter an edit mode (recursive minibuffer).  In '''Icicles''',
   [[Icicles - Cycling Completions|cycling]] replaces your input in the
   minibuffer by the current candidate, so you can just edit it there normally.  You can
   use `C-l' to retrieve your original input.



==== 6. Completions shown ====

In Ido, a limited number of matching
   completion candidates are shown in the minibuffer.  You can hit
   a key to see all matches in a separate buffer.

In '''Icicles''', completion candidates are always shown in buffer
   `*Completions*', not in the minibuffer.  You can limit the
   number of matches shown by customizing option '''`<tt>[[Icicles - Customization and General Tips#icicle-max-candidates|icicle-max-candidates]]</tt>''''.  Only the first
   `icicle-max-candidates' (in the current sort order) are shown.

You can also increment and decrement this truncation value on
   the fly during completion, by hitting '''`##C-x ###'''' and then using
   the vertical arrow keys or the mouse wheel.  (For that feature
   you also need library <tt>[[doremi.el]]</tt>.)



==== 7. Auto-choice of sole candidate ====

In Ido, if there is only one match for your input then `TAB',
   which normally completes, also chooses that candidate -- you do
   not need to hit `RET'.  By default, '''Icicles''' always requires you
   to explicitly choose, with `RET' (or `<tt>[[Icicles - Multi-Commands#HowDoesAMulti-CommandWork|C-RET]]</tt>').  If you set option '''`<tt>[[Icicles - Customization and General Tips#icicle-top-level-when-sole-completion-flag|icicle-top-level-when-sole-completion-flag]]</tt>'''' to non-`nil', then
   '''Icicles''' provides similar behavior to Ido.  See also option '''`<tt>[[Icicles - Customization and General Tips#icicle-top-level-when-sole-completion-delay|icicle-top-level-when-sole-completion-delay]]</tt>''''.




=== Ido-Like Behavior Everywhere: `icicle-ido-like-mode' ===

If you want '''Icicles''' to be Ido-like in general, then turn on global minor
mode '''`icicle-ido-like-mode'''' (not available in Emacs 20).  Doing
that sets options '''`<tt>[[Icicles - Customization and General Tips#icicle-show-Completions-initially-flag|icicle-show-Completions-initially-flag]]</tt>'''' and '''`<tt>[[Icicles - Customization and General Tips#icicle-top-level-when-sole-completion-flag|icicle-top-level-when-sole-completion-flag]]</tt>'''' to `t'.  Turning the
mode off sets them to `nil'.

You can simultaneously set option '''`<tt>[[Icicles - Customization and General Tips#icicle-max-candidates|icicle-max-candidates]]</tt>'''' when you turn
on `icicle-ido-like-mode', by using a positive [[prefix argument]].
If you want the option to keep that value when you turn the mode
off, then use a zero or negative prefix argument.  Otherwise, it
is reset to `nil' (no limit on the number of candidates displayed).

When you use this mode, you might also want to use `nil' or `t' as the
value of option '''`<tt>[[Icicles - Customization and General Tips#icicle-default-value|icicle-default-value]]</tt>'''', in order to not insert the
default value in the minibuffer.  If you want to change that
option dynamically for the mode, use `icicle-ido-like-mode-hook'.
E.g.:

  (add-hook 'icicle-ido-like-mode-hook
            (lambda () (setq icicle-default-value
                        (if icicle-ido-like-mode t 'insert-end))))




=== Ido-Like Behavior for Buffers and Files ===


If you want Ido-like behavior in '''Icicles '''for buffers or files, but
not in general, then customize either or both options '''`<tt>[[Icicles - Customization and General Tips#icicle-buffers-ido-like-flag|icicle-buffers-ido-like-flag]]</tt>'''' and '''`<tt>[[Icicles - Customization and General Tips#icicle-files-ido-like-flag|icicle-files-ido-like-flag]]</tt>'''' to
non-`nil'.





=== IswitchB-Like Behavior for `icicle-buffer' ===

As mentioned, you can use IswitchB with '''Icicles'''.  GnuEmacs
deprecated %%IswitchB%% starting with Emacs 24.4, but it is still
available.

If you want to get %%IswitchB%%-like behavior with '''Icicles'''
without using %%IswitchB%% then you can advise `icicle-buffer'.

There are at least two ways to do this, depending on what behavior
you want.  Let's assume that in any case (a) you want incremental
completion from the outset (no need to hit `TAB' or `S-TAB', and
(b) you want to Emacs to accept as your choice the sole candidate as
soon as you narrow matching to a single candidate.  For (a), you bind '''`<tt>[[Icicles - Customization and General Tips#icicle-incremental-completion|icicle-incremental-completion]]</tt>'''' to `always'.  For (b), you bind '''`<tt>[[Icicles - Customization and General Tips#icicle-top-level-when-sole-completion-flag|icicle-top-level-when-sole-completion-flag]]</tt>'''' to `t'.

1. In the first case, prefix completion is the default (as usual),
   but `icicle-buffer' uses vanilla Emacs completion as the
   Icicles `TAB' completion method.  This reflects %%IswitchB%%'s
   substring matching.  To do this, bind '''`<tt>[[Icicles - Customization and General Tips#icicle-current-TAB-method|icicle-current-TAB-method]]</tt>'''' to `vanilla'.

2. In the second case, `icicle-buffer' starts out with apropos
   completion, not prefix completion.  This too reflects
   %%IswitchB%%'s substring matching, but it extends it to regexp
   completion.  To do this, you bind '''`<tt>[[Icicles - Customization and General Tips#icicle-default-cycling-mode|icicle-default-cycling-mode]]</tt>'''' to `apropos'.

    ;; 1. Use vanilla Emacs matching for prefix completion by default.
    (defadvice icicle-buffer (around iswitchb-like-1 activate)
      (interactive)
      (let* ((icicle-current-TAB-method                   'vanilla)
             (icicle-incremental-completion               'always)
             (icicle-top-level-when-sole-completion-flag  't))
        ad-do-it))
    (ad-activate 'icicle-buffer)

    ;; 2. Start with apropos completion by default.
    (defadvice icicle-buffer (around iswitchb-like-2 activate)
      (interactive)
      (let* ((icicle-default-cycling-mode  'apropos)
                (icicle-incremental-completion  'always)
                (icicle-top-level-when-sole-completion-flag 't))
        ad-do-it))
    (ad-activate 'icicle-buffer)






'''See Also:'''

* [[Icicles - S-RET]]
* [[Icicles - Customization and General Tips]], options:
** `<tt>[[Icicles - Customization and General Tips#icicle-buffer-require-match-flag|icicle-buffer-require-match-flag]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-deletion-action-flag|icicle-deletion-action-flag]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-file-require-match-flag|icicle-file-require-match-flag]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-show-Completions-initially-flag|icicle-show-Completions-initially-flag]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-incremental-completion|icicle-incremental-completion]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-incremental-completion-delay|icicle-incremental-completion-delay]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-max-candidates|icicle-max-candidates]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-regexp-quote-flag|icicle-regexp-quote-flag]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-top-level-when-sole-completion-flag|icicle-top-level-when-sole-completion-flag]]</tt>'
** `<tt>[[Icicles - Customization and General Tips#icicle-top-level-when-sole-completion-delay|icicle-top-level-when-sole-completion-delay]]</tt>'

* [[Icicles - Completion Methods and Styles]]
* [[Icicles - Special Characters in Input Patterns]]
* [[Icicles - Nutshell View#PrefixAndAproposCompletion|Prefix Completion and Apropos Completion]]
* [[IciclesDiscussion#IdoAndIcicles|IciclesDiscussion]]
  (out-of-date discussion, but it might be helpful)



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DrewsElispLibraries referenced here: Lisp:icicles.el


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