### Piecewise function of several variables and how to display it

Hi,
I need to define a piecewise function of several variables. For a function of one variable I would use probably "Piecewise". I would like to work with a function G of two variables t and s that is of this form:

def G(t,s):
if (t < s):
return 1
else:
return 0

Although this works, I would like to have a nice displaying of this function, like a function generated by "Piecewise" does. Is there another way how to define this function?