Re: [Maxima-discuss] plotdf error, was: XMaxima in Maxima 5.40 seems broken in Windows and wxMaxima has issues

[Jaime V. <vi...@fe...>]

On 30-07-2017 22:12, Jaime Villate wrote:
> On 30-07-2017 20:02, Robert Dodier wrote:
>> Hmm, I don't understand what's going on here. number_of_arrows is only
>> used in Plotdf.tcl at:
>>
>> set stepsize [expr  { 420.0/sqrt($number_of_arrows) }]
>>
>> which used to be (pre-commit dca80e3) a constant value of 30. Obviously
>> number_of_arrows = 14^2  gives 30 again so that's great. But 15^2  gives
>> 28 and that gives an error -- what's wrong with that?
> .... why I never ran across that error after plotting thousands of 
> direction fields.

Now I understand what happened. The variable number_of_arrows and the 
statement
   set stepsize [expr {420.0/sqrt($number_of_arrows)}]
were added by Günter in March, when he applied a patched that a user 
named "themusicgod1"
sent him in the Debian launchpad site.

That guy seems to know Tcl, but in any case those kind of patches to a 
plotting program should never be committed without first making sure 
that at least the plots in the Manual still work.

Also, the patch sent by themusicgod1 to allow the user to change the 
number of arrows will only help those users who are Tcl hackers, because 
the regular Maxima users will not have any use for the new option 
number_of_arrows, unless it is also implemented in plotdf.lisp.

Regards,
Jaime