expression -- convert to an expression

• Usage:

  expression x

• Inputs:
  • x
• Outputs:
  • an expression, constructed from x using the mathematical structure of x, if present

i1 : egyptian = method();

i2 : egyptian QQ := x -> if x == 0 then 0 else (
     	    n := ceiling(1/x);
     	    expression(1/n) + egyptian(x - 1/n));

i3 : egyptian(30/31)

     1   1   1    1      1         1
o3 = - + - + - + --- + ----- + ---------
     2   3   8   107   15922   633759288

o3 : Expression of class Sum