user-defined function & string file name

[Taro S. <no...@gm...>]

Hello.  This is my first attempt at filing a potential bug report.=20
Please let me know if I'm doing something inappropriate here.=20
Especially if this is not a good place to do this, please point me to
the right direction.  I like the cvs version of gnuplot so much that
I'd like to keep submitting if I find any bugs in future.

It seems the gnuplot has difficulty distinguishing a user-defined
function and a string file name stored in a variable.  I have an ASCII
data file "xy.dat" with the following content:

BEGIN xy.dat-------------------
0       0
1.1     0.9
2.3     2.1
2.9     3.2
END----------------------

and wish to overplot a straight line.  If I do

BEGIN plot.okay.gp-------------------
reset
f(x) =3D x
plot f(x), 'xy.dat' u 1:2
pause -1
END----------------------

The plot comes out fine, but if I store the data file name in a string as i=
n

BEGIN plot.nogood.gp-------------------
reset
f(x) =3D x
fdat =3D 'xy.dat'
plot f(x), fdat u 1:2
pause -1
END----------------------

then gnuplot complains:

"plot.nogood.gp", line 4: warning: encountered a string when expecting a nu=
mber
"plot.nogood.gp", line 4: NB: you cannot plot a string-valued function

Thanks for your time,
Taro