data and function plot causing double assignment

[<pl...@pi...>]

Hi,

I have found what appears to be a defect in variable assignments in plot.

gauss0(x)=a0*exp(-(x-pk0)**2/b0)+c0
a1=a0;b1=b0;c1=c0;pk0=-141;
add_one(x)=area0=1;
plot  area0=0\
, datafile using 1:(add_one($2)) w l\
, datafile using 1:(($2)) w l\
, gauss0(x) tit 'fitted peak0'\

print "area0=",area0;

I was expecting this to do the assignment area0=0 once and once only 
before any of the lines were plotted.

It is only assigned once for the datafile plots but adding the function 
plot causes this snippet to print a value of zero , not one.

I am inferring that using a mix of data and function plots is causing 
the initial assignment to be done twice.  Bug or feature?

best regards, Peter.