Re: [ESPResSo] gnuplot

[Axel Arnold]

Hi,

Tcl quoting is a bit tricky... Your example should be

"set xrange \[0.9:0.91\]"

or

{set xrange [0.9:0.91]}

Basically, inside quotation marks, commands and variables are still expanded, 
while in curled braces, nothing happens. Therefore, while

"set xrange \[$start:$end\]"

would work, 

{set xrange [$start:$end]}

would not, since gnuplot would get "$start" and "$end" as boundaries.

So, there are three types of quotations/brackets in Tcl:

1. {}: embraces a raw string, contents are kept character by character
2. "": embraces a string, in which [] (command substitution) and $ (variable 
substitution) are evaluated
3. []: command substitution: as "", but the content is evaluated as Tcl 
expression, and [...] replaced by the result of this command

As usual, a \ can be used to prevent the evaluation of [] or $, but unlike in 
many other languages, single quotes have no special meaning in Tcl. Something 
like

set test 'a b'

causes an error, because you try to assign two separate values, <'a> and <b'>, 
to test.

Axel

On Tuesday 04 May 2010 11:10:52 Guillaume Larsen wrote:
> Hi Olaf,
>
> nope, the problem still persists.
>
> Guillaume
>
> > Date: Tue, 4 May 2010 11:04:43 +0200
> > From: address@hidden
> > To: address@hidden
> > Subject: Re: [ESPResSo] gnuplot
> >
> > Quoting Guillaume Larsen <address@hidden>:
> > > I have a slight problem concerning the plotObs function of ESPResSo.
> > > When I try to pass gnuplot arguments to specify a restricted range,
> > > for instance 'set xrange [0.9:0.91]', ESPResSo tries to evaluate
> > > what is between the brackets [] and thus returns an error, saying
> > > that '0.9:0.91' is not a valid command name.
> > > How to avoid this problem?
> >
> > Try "set xrange '[0.9:0.91]'"
> >
> > Olaf
> >
> > ----------------------------------------------------------------
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> >
> >
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-- 
Dr. Axel Arnold Tel: +49 711 685 67609
ICP, Universität Stuttgart      Email: address@hidden
Pfaffenwaldring 27
70569 Stuttgart, Germany