[Maxima-discuss] numerics, NaNs, etc

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

Consider these definitions:
u(x):= 2*x/(1+x)$
v(x):= 2- (2/x)/(1+1/x)$
w(x):= (1+u(x)^2)/(2+u(x)^2)$
y(x):= (1+v(x)^2)/(2+v(x)^2)$
z(x):= 1-1/(2+v(x)^2)$
ll(x):= [u(x),v(x),w(x),y(x),z(x)]$

Now if we try:

ratsimp(ll);
we see that u=v,  w=y=z    as rational functions.

try ll(1/2) for instance. Looks OK.

but ll(0) fails with  expt: undefined 0 to a negative exponent.
.
If you load my infinity.lisp file and try
ll(rat(0))  you get [0, indef, 1/2,indef, oo]
...
This example comes from
https://people.eecs.berkeley.edu/~wkahan/UnumSORN.pdf
RJF