Re: gnuplot-4.4.0-rc1 breaks gnuplot script

[Teo S B. <teo...@gm...>]

I gave an argument for allowing trailing definitions at bottom of
http://article.gmane.org/gmane.comp.graphics.gnuplot.devel/9253

On Sun, Feb 14, 2010 at 9:24 PM, Ethan Merritt <merritt@u.washington.edu> wrote:
> On Sunday 14 February 2010, Teo S Bernhard wrote:
>> historic gnuplot implementations. See the brief usage instruction:
>>      plot {<ranges>}
>>              {<iteration>}
>>              {<function> | {"<datafile>" {datafile-modifiers}}}
>>              {axes <axes>} {<title-spec>} {with <style>}
>>              {, {definitions{,}} <function> ...}
>
> You are not interpreting this BNF description correctly.
> The meaning of the final line quoted immediately above is
>  "If you append a comma you must follow it with a function.
>   The function may optionally be preceded by a definition,
>   with or without a separating comma."
>
> The <function> element is not in curly brackets, and hence is
> not optional.  There is no expansion of this set of BNF rules that
> results in a trailing definition.  So no, the documentation
> has never stated that a trailing definition was valid syntax.

Agreed, but strict interpretation of this BNF does also tell that
initial definitions are disallowed. This contradicts a given example
of 'help plot' (version 4.2).

                     plot f(x) = sin(x*a), a = .2, f(x), a = .4, f(x)

Given also that the help text of gnuplot 4.2 says, from 'help plot':
   "It is also possible to define functions and parameters on the `plot` command
   itself.  This is done merely by isolating them from other items with commas."

The implementation of gnuplot 4.2 and 4.3 allows in a quite liberal
form definitions at both leading and trailing end of the plot command
as long a they are separated by comma, example:
              plot f(x) = sin(x*a), a = .2, f(x), a = .4, f(x), a=0.6

IMHO, the stated BNF contradicts other parts of the help text and also
the actual code-implementation.

For the historic (pre 4.4 rc1) gnuplot versions, a BNF consistent with
other help text and code-implementation (considering definitions
mainly) should be roughly:

     plot {<ranges>}
             {<iteration>}
             {definitions,}...
             { <function> | {"<datafile>" {datafile-modifiers}}}
             {axes <axes>} {<title-spec>} {with <style>}
             {,definitions}...  {,<function>... }

It is obviously a philosophical point, if implementation or
documentation should govern.
I think the historical implementation in this case.

Teo