Re: user-defined function & string file name

[Ethan A M. <merritt@u.washington.edu>]

On Tuesday 28 June 2005 08:34 am, Hans-Bernhard Br=F6ker wrote:
> Taro Sato wrote:
> >
> > f(x) =3D x
> > fdat =3D 'xy.dat'
> > plot f(x), fdat u 1:2
> > "plot.nogood.gp", line 4: warning: encountered a string when expecting
> > a number "plot.nogood.gp", line 4: NB: you cannot plot a string-valued
> > function
>
> This is not exactly a bug, but a known syntactical limitation.  The way
> around it is to drop the parser a hint that fdat is meant to be a
> string, not a number, like this:
>
>     plot f(x), ''+fdat u 1:2    # or was that ''.fdat  ?

The string concatenation operator is .  so the hint would be ''.fdat

However, I think this really is a bug.  `plot f(x)` and `plot fdat`
both work individually; it is only the combination of the two that
triggers an error message.  That should be fixable.  I suspect that
whatever causes this will also turn out to explain a problem in one of Juer=
gen Wieferink's patches.

The difficult case (which this is not an example of) is distinguishing
a user-defined function that returns the name of a file from a user-
defined function that returns a numerical value.

=2D-=20
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742