Can't evaluate limits of piecewise

[Illuminati-CRAZ]

The version I use: AngouriMath/AngouriMath.Interactive

Unexpected behaviour or bug:

[WhiteBlackGoose]

Um... I'm not sure... if this even has a limit, since there's a jump discontinuity at x = 0

[WhiteBlackGoose]

Ah, so it returned a limit. Correct, I see. But for the other cases... well, there definitely are limits, and it didn't find it. I see. That's kind of bug, but... as well as a missing feature

[Rafael-SOWNet]

Fixed in #714, on master now.

Two causes sat on top of each other. The gate at the top of ComputeLimit admits ContinuousNode only, and a Piecewise is not one, so the descent's Piecewise case was never reached. And that case was dead anyway: it tested allLims.Select(c => c.lim is null).Any(), which is Any() with no predicate -- "is the sequence non-empty" -- so it always returned null. Even had it run, it built a piecewise of the cases' limits carrying predicates that still speak about the variable the limit had just removed.

It now picks the case that holds near the destination, reading each predicate from the sign its comparisons keep on the way in. With the piecewise from your screenshot:

lim x->0-    =>  -1
lim x->0+    =>   1
lim x->0     =>  NaN     (the two sides disagree, so there is no limit)
lim x->-456  =>  -1
lim x->123   =>   1

Closing.