Help with Piecewise function

[salvomic]

hi,
I would like to evaluate "square wave" functions (also with Fourier series...), so I create a "piecewise" function:
f(t):=PIECEWISE(-π<t<0,-1,t=0,0,t=-π,0,t=π,0,0<t<π,1)
The interval of values is -pi < t < pi and the function is constant (1 or -1) except in 0, π, -π

If I try f(-4) I get 1 but I should get "No case applies", I think...
f(-3) also 1, but it should be -1
and so on...
I input integrate(f(t),x,-pi,pi) and I get "No case applies"...

Please, help me to find where is the error... Sure I didn't understand how to use "pisewise()"; I read the help...

Salvo