Patch to make ic2 work even with i.c. 'y(x)= (fwd)

On Tue, 3 Feb 2009, Billinghurst, David (RTATECH) wrote:
>> From: Robert Dodier
>>
>> On 1/30/09, Christophe Deroulers wrote:
>>
>>>   This is a patch proposal / feature request.
>>>
>>>   In brief:
>>>   ---------
>>>   Change subs([xa,ya],soln) to subs([ya,xa],soln) in the
>> line 318 of
>>> the file share/diffequations/ode2.mac .
>>>
>>>   This would allow initial conditions like 'y(x)=2 (for an O.D.E.
>>> written like "... + 'y(x)= 0") in addition to initial
>> conditions like
>>> y=2 (for an O.D.E. written like "... + y = 0").
>>
>> OK by me if we can verify that the proposed patch doesn't
>> change the behavior of the ODE code for existing problems.
>> There is a large test suite for Maxima's ODE code -- I don't
>> know how much (if any) calls the function touched by the patch.
>> Perhaps you, Christophe, can look into it and report on it.

  Thank you, Robert, for your interest. What you propose sounds good to me.

David:
> There are only two tests of ic2 in the testsuite, and none in
> the share/contrib/diffequations testsuite.  I think we need
> more before we can be sure there are no adverse effects.

  Indeed, there are 37 tests involving ode2 but only 2 involving ic2. Maybe 
the first thing to do would be to add more tests calling ic2 (ideally one 
test of ic2 for each test of ode2)? Then one could go ahead with the 
patch. I'll see if I can do that.

  Best wishes,

   Christophe Deroulers
University Paris Diderot-Paris 7