13 Notes: Booleans and Comparisons.sml

(* boolen expressions *)

(* e1 andalso e2
 	if e1 is false, we do not evalutate e2

	
    e1 orelse e2

    if we get true for e1, we evaluate e2,
    otherwise we don't 	


    **andalso and orelse are not functions*

 *)

(* if a language has if-then-else constructs 
   => we do not  _need_ andalso, orelse, not 
	
	example:

	e1 andalso e2 is equivalent to:

	if e1 
	then e2
	else false
	
	etc.  But that is bad style.

*)



(* 

Comparison operators (for int):

   =   
   <>   not equal
   > 
   <
   >=
   <=

   ----> we can't use the last 4 operators can between an int and a real
   ----> use for example,  Real.fromInt 2;  
   ----> we can NOT use = and <> on floating point numbers (real)
         which is actually a good practice as 'real' is not an 'equality type'
         we have issues comparing floats with each other due to rounding off, precision etc.
                              

   *)