Help with Piecewise function

[Snorre]

Hello,

I think, the Prime doesn't understand "0<t<π" the way you'd expect.
It does a (0<t)<π, which means: if the result of (0<t) -- a boolean 0 or 1 -- is less than π -- which is always true -- then ...

Just write "0<t AND t<π".

Furthermore, there's no "else" case (so f(-4) would be undefined if written with ANDs, but is catched by the always-true (0<t)<π).
I think your function should look more like:

f(t):=piecewise(-π<t and t<0,-1, 0<t and t<π,1, 0)

Greetings