Re: gnuplot-4.4.0-rc1 breaks gnuplot script

[sfeam (E. Merritt) <eam...@gm...>]

On Sunday 14 February 2010, Hans-Bernhard Bröker wrote:
> > On Friday 12 February 2010 11:26:36 Teo S Bernhard wrote:
> 
> >>>> the below shortened example reproducing the error message:
> >>>>
> >>>>
> >>>> # file: trial.gpl
> >>>> f(x)=x
> >>>> plot a=1, \
> >>>>      f(x)*a   title "data from index a=1" w l lw 2 lt a ,  a=a+1,       \
> >>>>      f(x)*a   title "data from index a=2" w l lw 2 lt a ,  a=a+1,       \
> >>>>      a=0 
> 
> I see no particularly compelling reason why this can't be changed to
> 
> a=0 ; plot \
>       f(x)*a   title "data from index a=1" w l lw 2 lt a ,  a=a+1, \
>       f(x)*a   title "data from index a=2" w l lw 2 lt a ; a = 0
> 
> Note the semicolons.

The problem is that the two forms do not produce the same result.
See Bug #2907028.

If you place the "a=0" inside the plot statement, 
then a really is 0 during the first function evaluation.  
If you place the "a=0" before the plot statement, separated by a semicolon, 
then a has the value 1 during the first function evaluation.
This is, to say the least, unexpected.