all the prefix arguments do the same thing

all the prefix arguments do the same thing

[Dan Jacobson]

Gentlemen, let's examine
    ESC | runs the command shell-command-on-region

    Execute string COMMAND in inferior shell with region as input.
    Normally display output (if any) in temp buffer `*Shell Command Output*';
    Prefix arg means replace the region with it.

Well, how about let's say one doesn't want to replace the region, nor
put it in a separate buffer, but instead insert the output above or below
the region?

Currently any prefix argument means "replace".   Do you think just
maybe you could make some certain prefix arguments do what I want?

Don't you think it isn't smart to make _all_ the prefix arguments do
the same thing?  Isn't that a lazy bad habit that will only bite you
back later when you want to add new actions?

Emacs is littered with this... Why didn't Stallman think ahead... What
if all the TCP ports pointed to the same service?

In the future, OK, a new command should at least use 4 (C-u) and maybe
1 to do the default "when given an argument" thing, but say 98 should
trigger an error if it hasn't been purposely implemented yet -- in
case somebody expects to do special argument 98's function on an older
version that doesn't support it.  Better trigger an error that have
the user think things went smoothly.
-- 
http://jidanni.org/ Taiwan(04)25854780

Re: all the prefix arguments do the same thing

[Richard Stallman]

    Well, how about let's say one doesn't want to replace the region, nor
    put it in a separate buffer, but instead insert the output above or below
    the region?

    Currently any prefix argument means "replace".   Do you think just
    maybe you could make some certain prefix arguments do what I want?

I think that would be creeping featurism.  You can duplicate the region
before you run M-| and get the results you want.