Re: Scoping of variables in block constructs

[Ethan A M. <sf...@us...>]

On Monday, 09 October, 2017 20:19:43 Achim Gratz wrote:
> sfeam via gnuplot-beta writes:
> > Too complicated for me to work through in detail but one line
> > is waving a red flag.   This line
> >      set ytics @ticdef
> > is almost certainly not what you want to do.
> 
> Ah, OK.
> 
> > The macro expansion operator @ is like a #define statement in C.
> > It causes a substitution at the time the file/block/clause/program unit
> > is read in.  It is _not_ reevaluated at run time.
> 
> I still can't quite figure out the consitions under which this was and
> wasn't working for my example in various stages of its development, but
> I think that must be the right explanation.
> 
> > An example of evaluation at run time would be:
> >
> >    ... loop that constructs ticdef ...
> >    eval "set ytics " . ticdef
> 
> This seems all unnecessarily involved, so maybe I should rather ask if
> there's a way to build up an explicit tics list piece by piece rather
> than having to feed everyting as one single giant string?

Yes.   The keyword "add" does what you want.

	# x labels at 1 2 3 ... and also at certain interesting values
	array label[4] = ["sqrt(2)", "sqrt(3)", "e", "pi"]
	array value[4] = [1.414, 1.732, exp(1), pi]
	set xtics 1.0
    do for [i=1:4] {
		set xtics add (label[i] value[i])
    }
	
> Also, why is there no block "else if" or maybe even "elsif"?

No particular reason.  
So far as I can see, all it would gain is to reduce the number of 
required curly brackets by one pair.
Is there something more subtle I'm missing?

	Ethan

> 
> Regards,
> Achim.
>