Re: gnuplot-4.4.0-rc1 breaks gnuplot script (patch)

[Ethan M. <merritt@u.washington.edu>]

On Saturday 13 February 2010, Teo S Bernhard wrote:
> On Fri, Feb 12, 2010 at 7:07 PM, Ethan Merritt <merritt@u.washington.edu> wrote:
> >
> > On Friday 12 February 2010 09:58:45 Teo S Bernhard wrote:
> > > Problem:
> > > Gnuplot script that set parameter repeatedly in plot command to address the
> > > data index (within a data file) does not work when using gnuplot version
> > > 4.4.0-rc1.
> > > It works in 4.2 version and, from memory, did also work in version 4.3. See
> > > 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
> >
> > Please see Bug #2907028
> >  https://sourceforge.net/tracker/?func=detail&aid=2907028&group_id=2055&atid=102055
> >
> > So far as I can tell from running old versions of gnuplot (back to 3.7),
> > it never did work correctly to increment a variable multiple times inside
> > a plot command.
> 
> I have looked into the code, plot2d.c, regarding this issue. I have a
> suggestion for a patch that seems to:
> 1)  solve referred Bug #2907028
> 2)  also allow trailing assignments to the plot command.
> 
> There are spurious print-outs in the patch, I have assumed the
> intuitive meaning of END_OF_COMMAND.
> The purpose of the 'was_definition' flag is not clear to me, I set it
> to TRUE always since I belive that the
> result of is_definition(...)  would guarantee this.
> 
> I have tested it on small examples similar to those presented in this thread.
> Review and comments on the conceptual idea as presented below in a
> diff-form are appreciated.

The first pass is used for plotting data, 
the second pass is used for evaluating functions.
If you disable definitions in the first pass, 
you break plotting from a file.  Consider

 plot col=2, 'data' using 1:col with lines

If you want to pursue this, you will need to use test cases
that mix both function plots and data plots.

	Ethan

> 
> Teo
> --------------------------------
> Diff agains gnuplot-4.4.0-rc1, 'hg diff' was run in ./src-directory:
> 
> diff -r 9c57e57e6e92 plot2d.c
> --- a/plot2d.c	Fri Feb 12 22:35:43 2010 +0100
> +++ b/plot2d.c	Sat Feb 13 14:23:04 2010 +0100
> @@ -1457,12 +1457,29 @@
>  	    newhist_pattern = fs.fillpattern;
>  	} else
> 
> -	if (is_definition(c_token)) {
> -	    define();
> -	    if (!equals(c_token,",")) {
> -		was_definition = TRUE;
> -		continue;
> -	    }
> +        if (is_definition(c_token)) {   /*skip over definitions in first pass*/
> +          if (1==0){ /*original version that evaluate definitions
> also in first pass*/
> +            printf("fp: original: definition for c_token: %i\n", c_token);
> +            define();
> +            printf("fp: original:         done,  c_token: %i\n", c_token);
> +            if (!equals(c_token,",")) {
> +                 was_definition = TRUE;
> +                 continue;
> +            }
> +          }
> +          else { /*modified version that skips definitions in first pass*/
> +            was_definition = TRUE;
> +            printf("fp: modified: definition for c_token: %i\n", c_token);
> +            while(!END_OF_COMMAND && !equals(c_token,",")){
> +              c_token++;
> +            }
> +            printf("fp: modified:         done,  c_token: %i\n", c_token);
> +            if (END_OF_COMMAND){
> +              printf("fp: END_OF_COMMAND: %i\n", END_OF_COMMAND);
> +              break;
> +            }
> +          }
> +
> 
>  	} else {
>  	    int specs = 0;
> @@ -2172,12 +2189,28 @@
>  	    if (!in_parametric && !was_definition)
>  		start_token = c_token;
> 
> -	    if (is_definition(c_token)) {
> +	    if (is_definition(c_token)) { /*do definitions on second pass */
> +	      if (1==0){ /*original version*/
> +		printf("sp: original: definition for c_token: %i\n", c_token);
>  		define();
> +		printf("sp: original:         done,  c_token: %i\n", c_token);
>  		if (!equals(c_token,",")) {
>  		    was_definition = TRUE;
>  		    continue;
>  		}
> +	      }
> +	      else { /*modified version does definitions and allows a trailing one*/
> +		printf("sp: modified: definition for c_token: %i\n", c_token);
> +		define();
> +		was_definition = TRUE;
> +		printf("sp: modified:         done,  c_token: %i\n", c_token);
> +		if (END_OF_COMMAND){
> +		  printf("sp: END_OF_COMMAND: %i\n", END_OF_COMMAND);
> +		  break;
> +		}
> +	      }
> +
> +
> 
>  	    } else {
>  		struct at_type *at_ptr;
> 
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