CSE526: Principles of Programming Languages
			      Scott Stoller
       solution to hw2: denotational semantics in ocaml, part 2
			version: 9pm,23feb2004
			   due: 19 feb 2004

PROBLEM 1

type entry = { var : string ; value: int }
type t = entry list

let state_zero = []

let rec get_value sigma v = 
  match sigma with
  [] -> 0
  | y::l -> if y.var = v then y.value else get_value l v

let rec update sigma v i = 
  match sigma with
  [] -> [{ var = v ; value = i }]
  | y::l -> if y.var = v then { var = v ; value = i }::l
	    else y::update l v i



PROBLEM 2

type entry = { var : string ; mutable value: int }
type t = entry list

let state_zero = []

let rec get_value sigma v = 
  match sigma with
  [] -> 0
  | y::l -> if y.var = v then y.value else get_value l v

let rec update sigma v i = 
  match sigma with
  [] -> [{ var = v ; value = i }]
  | y::l -> if y.var = v then ( y.value <- i ; y::l )
	    else y::update l v i