NaNs not propagating

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

Hi,

I seem have a problem with NaN not propagating to function calls.


gnuplot>

  integ(x)=(int_last==0)?(NaN,int_last=x):(int_last=int_last+x)

plot int_last=0, "-" u 1:(integ($2-44)) w l
input data ('e' ends) > 1 1
input data ('e' ends) > 2 2
input data ('e' ends) > 3 NaN
input data ('e' ends) > 4 4
input data ('e' ends) > 5 5
input data ('e' ends) > e

gnuplot> print int_last+NaN
NaN


This gives a straight line with a break which means that the third line 
is evaluating NaN as zero and passing -44 to the function.

I was expecting the argument (NaN-44) to pass NaN to the function which 
would in turn return and assign a NaN  leaving all further points 
unplotted.


Bug or feature ?

Regards, Peter.