#3345 bug in limit

[Dimiter Prodanov]

The following

limit(( %e^(-sqrt(2*s-1)*atan(y))) , s, inf);

gives an error

The value #:|cos(0)3749| is not of type LIST.
Automatically continuing.
To enable the Lisp debugger set *debugger-hook* to nil.

wxMaxima version: 17.05.0
Maxima version: 5.38.1
Maxima build date: 2016-06-12 17:13:34
Host type: i686-pc-mingw32
System type: Win32 6.1.7601 (Service Pack 1) X86-64
Lisp implementation type: SBCL
Lisp implementation version: 1.3.4

[Raymond Rogers]

[Kris Katterjohn]

added some tildes to fix the formatting

[Raymond Toy]

Bizarre that the atan(y) term messes things up. If you leave it off, limit returns 0. Replacing atan(y) with just y allows limit to succeed.

[David Scherfgen]

In Maxima 5.50post (SBCL 2.6.7) this limit no longer signals "The value #:|cos(0)NNNN| is not of type LIST". It now asks for the sign of y and returns 0 for positive y and inf for negative y, which is correct because sqrt(2*s-1) -> +inf while the exponent's sign is that of -atan(y). Supplying the sign in advance avoids the question: assume(y>0) gives 0 and assume(y<0) gives inf.

(%i2) limit(( %e^(-sqrt(2*s-1)*atan(y))) , s, inf);
Is y positive, negative or zero? pos;
(%o2) 0

Verified by Claude.