Re: [Maxima-discuss] complex numbers in Maxima and lisp / a warning?

[Richard F. <fa...@be...>]

maybe lisp #c(1 3)   should print in Maxima as  escaped lisp...
e.g.   ?complex(1,3)

Actually, typing k: ?complex(1,3)  is an even simpler way to create k.

Along these lines, is there any reason to print   ?foo(x)   as foo(x)?   
It is
hard to explain the display  foo(x)-?foo(x).

Internally  there are two function names, distinct.
$foo and foo.    Externally, why not  use foo  and ?foo for them?

And for the rational number created in Lisp by typing 3/4 we could
display  ?/(3,4), rather than making believe it is the same as Maxima's 3/4.

At least until, as Ray says, everything works the same regardless.


So here's the proposal, which should break nothing that already exists:

change nformat so that  lisp ((foo) ....)  is printed as  ?foo( ....)
change nformat and/or wxformat so that common lisp #c(1 3) is printed as 
?complex(1,3)
change nformat and/or wxformat so that common lisp 3/4 is printed as ?/(3,4)

Oh, why I care ... messing around with intervals, computing sqrt( 
[-2,2]) produced complex
numbers, but I was not prepared for non-real results....

FYI,   I thought this could all be fixed by changing a function in 
suprv1.lisp called
appropriately enough,   stripdollar.   So I traced it. Not the answer.

More later.


Richard


On 3/31/2016 11:19 AM, Raymond Toy wrote:
>>>>>> "Richard" == Richard Fateman <fa...@be...> writes:
>      Richard> It is possible to construct complex numbers in lisp  (though so far we have
>      Richard> mostly avoided it....) . The simplest way is
>
>      Richard> :lisp   (setf $k #c(1 3)
>
>      Richard> now
>      Richard> k;  prints as 3 %i+1
>
> I wish maxima didn't do that.  Well, as long as maxima doesn't really
> operate with Lisp complex numbers.
>
>      Richard> however,  k -3*%i -1
>      Richard> prints as 0 + 3 %i - 3 %i.
>
>      Richard> There are other anomalies, such as
>
>      Richard> ratcoef(k,%i) returns 0.
>      Richard> k+1/2 signals an error.
>      Richard> sin(k) signals an error
>
> We should probably fix those.  For k+1/2, the error comes from trying
> to print k+1/2 which has somehow been computed as ((rat simp) #c(3 6)
> 2) and printing wants to compare #c(3 6) with 0.
>
> sin(k) fails trying to apply the reflection formula and ends up
> comparing (in lisp) #c(-2 -6) and 0.  I have no idea where the #c(-2
> -6) comes from.
>
> --
> Ray
>
>