Re: Defining functions on the fly

["Andreas Röhler" <andreas.roehler@easy-emacs.de>]

Am 16.06.2015 um 11:50 schrieb Pascal J. Bourguignon:
> Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
>
>> Am 16.06.2015 um 09:01 schrieb Tassilo Horn:
>>> Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
>>>
>>>>>> i'm probably misunderstanding you, but does:
>>>>>>       (defun (intern (concat "current-prefix-" foo) ...
>>>>>> do what you need?
>>>>> (defalias (intern (concat "current-prefix-" foo) ...) ...) can work, but
>>>>> not with defun.  In any case, some concrete example of what he needs to
>>>>> do would go a long way.
>>>>>
>>>>>
>>>>>            Stefan
>>>> Currently Emacs provides some scheme to fontify source code and some
>>>> basic moves: linewise, symbol, word, paragraph, sexp.
>>>>
>>>> There is no idea of statement, block/loop or expression and a poor
>>>> top-level --beginning/end-of-defun.
>>> There is: `forward-sexp' and `backward-sexp'.  Although the name sexp is
>>> a bit lisp-specific, sexp-based motion has been implemented for more
>>> C-like languages, too.  For example, it works well for shell scripts
>> Unfortunatly couldn't experience this. There are several common cases
>> within shell-script, where calls to navigate sexp would raise an
>> error.
>>
>> That's why language-modes have to implement a couple of most basic
>> things. See
>>
>> http://lists.gnu.org/archive/html/emacs-devel/2015-06/msg00013.html
>>
>> ###
>>
>> vorhanden() {
>>      for i in "blah" "blub";
>>      do
>>          # some comment (note: for compatibility)
>>      if [ ! -x $i ]; then
>>
>> ###
>>
>> with cursor last line "if", C-M-b jumps to "for", but should end at "do"
>>  From "for" ->
>>
>> Debugger entered--Lisp error: (scan-error "Containing expression ends
>> prematurely" 13 13)
>>    signal(scan-error ("Containing expression ends prematurely" 13 13))
>>    smie-forward-sexp-command(-1)
>>    forward-sexp(-1)
>>    backward-sexp(1)
>>    call-interactively(backward-sexp nil nil)
>>    command-execute(backward-sexp)
>>
>> There are many more spots in this example to trigger error or
>> unexpected moves.
>>
>> Or take this:
>>
>> ###
>>
>> if [ $# == 0 ]; then
>>      # some comment (note: for compatibility)
>>      set "" `find .  -maxdepth 1 -type f -name "*.txt" | sed
>> s/..\(.*\)/\1/'`
>>
>>      for i in $*; do
>>          # some comment (note: for compatibility)
>>      pass
>>      done
>>
>> fi
>>
>> ###
>>
>> With cursor at third line, "set", expression is not recognised at all,
>> C-M-f stops at the end of symbol "set"
>>
>> That's a fakir's mode :)
> There are hooks to customize those general commands to specific modes!
> For example, instead of writing:
>
>      bash-forward-sexp
>      sh-forward-sexp
>      pascal-forward-sexp
>      ada-forward-sexp
>
> etc, each mode will just bind a specific forward sexp function to the
> hook variable:  forward-sexp-function, and forward-sexp will call it.
>
>

That's a consideration at the command- resp. key-binding level.
Nonetheless mode-specific functions are needed to bind then.

For now these language mode often invent very basic things in parallel: 
string-strip, in-string-p etc.
Also creating bugs and quirks that way.

Beyond that we can generalize top-level, block, expression and statement 
-- at least to some extend.