Re: Executing part of the code instead of another

[Christopher Dimech <dimech@gmx.com>]

Noted Nick.  Thank you.

---------------------
Christopher Dimech
Chief Administrator - Naiad Informatics - GNU Project (Geocomputation)
- Geophysical Simulation
- Geological Subsurface Mapping
- Disaster Preparedness and Mitigation
- Natural Resource Exploration and Production
- Free Software Advocacy


> Sent: Wednesday, October 07, 2020 at 7:29 PM
> From: "Nick Dokos" <ndokos@gmail.com>
> To: help-gnu-emacs@gnu.org
> Subject: Re: Executing part of the code instead of another
>
> Christopher Dimech <dimech@gmx.com> writes:
>
> > I have tried executing the following condition (if (nb > na))
> >
> > (setq na 2)
> > (setq nb 5)
> > ( if (> nb na)
> >     (message "nb > na [condition true]")
> >     (message "condition false")
> > )
> >
> > I highlighted the region then pressed C-x C-e
> > It returned the first message as expected, but when I tried
> > the next one, I still got the first message.
> >
> `C-x C-e` is bound to `eval-last-sexp` which evaluates the *last*
> sexp: the if.  It does not evaluate the setq's (setting the region does
> *NOT* matter for it - try `M-x eval-region' for that)
>
>
> > (setq na 2)
> > (setq nb 1)
> > ( if (> nb na)
> >     (message "nb > na [condition true]")
> >     (message "condition false")
> > )
> >
> >
> >
> >
> >> Sent: Wednesday, October 07, 2020 at 9:20 AM
> >> From: "Robert Pluim" <rpluim@gmail.com>
> >> To: "Christopher Dimech" <dimech@gmx.com>
> >> Cc: moasenwood@zoho.eu, help-gnu-emacs@gnu.org
> >> Subject: Re: Executing part of the code instead of another
> >>
> >> >>>>> On Wed, 7 Oct 2020 09:01:00 +0200, Christopher Dimech <dimech@gmx.com> said:
> >>
> >>     Christopher> What can one use if there is an else branch with multiple commands, as I would
> >>     Christopher> like to use it.
> >>
> >> From 'C-h f if'
> >>
> >>     if is a special form in `C source code'.
> >>
> >>     (if COND THEN ELSE...)
> >>
> >>       Probably introduced at or before Emacs version 1.1.
> >>
> >>     If COND yields non-nil, do THEN, else do ELSE...
> >>     Returns the value of THEN or the value of the last of the ELSE's.
> >> =>  THEN must be one expression, but ELSE... can be zero or more expressions.
> >>     If COND yields nil, and there are no ELSE's, the value is nil.
> >>
> >>
> >> Robert
> >> --
> >>
> >
> >
>
> --
> Nick
>
> "There are only two hard problems in computer science: cache
> invalidation, naming things, and off-by-one errors." -Martin Fowler
>
>
>