New user-defined variables and functions of one through five variables may
 be declared and used anywhere.

 User-defined function syntax:
          (  {, {, ...} } ) = 

 where  is defined in terms of  through .

 User-defined variable syntax:
          = 

 Examples:
         w = 2
         q = floor(tan(pi/2 - 0.1))
         f(x) = sin(w*x)
         sinc(x) = sin(pi*x)/(pi*x)
         delta(t) = (t == 0)
         ramp(t) = (t > 0) ? t : 0
         min(a,b) = (a < b) ? a : b
         comb(n,k) = n!/(k!*(n-k)!)
         len3d(x,y,z) = sqrt(x*x+y*y+z*z)

 Note that the variable pi is already defined.

 See  show functions and  show variables.