Oct 6, 2003
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- More functions
	- writing a recursive square function
	- writing a powerset function
	- using a "let" inside it
		- to prevent recomputing
	- composing functions

- Codes written today

fun square(0) = 0
|   square(x) = square(x-1) + 2*x -1;

fun inserteverywhere(x,nil) = nil
|   inserteverywhere(x,L::Ls)
  = (x::L)::inserteverywhere(x,Ls);

fun powerset([]) = [nil]
|   powerset(x::xs) =
	let 
           val y = powerset(xs)
	in
           inserteverywhere(x,y)@y
	end;

fun f1(x) = x+2;
fun f2(x) = x*3;

fun identity(x) = x;

fun cool(F,G) =
	let
		fun C(x) = G(F(x))
	in
		C
	end;

val C = cool(f1,f2);

C(3);

val D = cool(f2,f1);

D(3);