diff --git a/compile.rkt b/compile.rkt
index 9324a5d..e12e238 100644
--- a/compile.rkt
+++ b/compile.rkt
@@ -1,6 +1,8 @@
 #lang typed/racket/base
 
-(require "typed-structs.rkt"
+(require "expression-structs.rkt"
+         "lexical-structs.rkt"
+         "il-structs.rkt"
          "lexical-env.rkt"
          "helpers.rkt"
          "find-toplevel-variables.rkt"
@@ -202,31 +204,7 @@
           after-lambda)))
 
 
-(: collect-lexical-references ((Listof LexicalAddress) 
-                               -> 
-                               (Listof (U EnvLexicalReference EnvWholePrefixReference))))
-;; Given a list of lexical addresses, computes a set of unique references.
-;; Multiple lexical addresses to a single prefix should be treated identically.
-(define (collect-lexical-references addresses)
-  (let: ([prefix-references : (Setof EnvWholePrefixReference) (new-set)]
-         [lexical-references : (Setof EnvLexicalReference) (new-set)])
-        (let: loop : (Listof (U EnvLexicalReference EnvWholePrefixReference)) 
-              ([addresses : (Listof LexicalAddress) addresses])
-              (cond 
-                [(empty? addresses)
-                 (append (set->list prefix-references) (set->list lexical-references))]
-                [else
-                 (let ([addr (first addresses)])
-                   (cond
-                     [(LocalAddress? addr)
-                      (set-insert! lexical-references
-                                   (make-EnvLexicalReference (LocalAddress-depth addr)
-                                                             (LocalAddress-pos addr)))
-                      (loop (rest addresses))]
-                     [(PrefixAddress? addr)
-                      (set-insert! prefix-references
-                                   (make-EnvWholePrefixReference (PrefixAddress-depth addr)))
-                      (loop (rest addresses))]))]))))
+
 
   
 
diff --git a/expression-structs.rkt b/expression-structs.rkt
new file mode 100644
index 0000000..df8a6f2
--- /dev/null
+++ b/expression-structs.rkt
@@ -0,0 +1,36 @@
+#lang typed/racket/base
+(require "lexical-structs.rkt")
+
+(provide (all-defined-out))
+
+;; Expressions
+
+(define-type ExpressionCore (U Top Constant Var Branch Def Lam Seq #;App))
+(define-type Expression (U ExpressionCore #;Assign))
+
+(define-struct: Top ([prefix : Prefix]
+                     [code : ExpressionCore]) #:transparent)
+(define-struct: Constant ([v : Any]) #:transparent)
+(define-struct: Var ([id : Symbol]) #:transparent)
+(define-struct: Assign ([variable : Symbol]
+                        [value : Expression]) #:transparent)
+(define-struct: Branch ([predicate : Expression]
+                        [consequent : Expression]
+                        [alternative : Expression]) #:transparent)
+(define-struct: Def ([variable : Symbol] 
+                     [value : Expression]) #:transparent)
+(define-struct: Lam ([parameters : (Listof Symbol)]
+                     [body : Expression]) #:transparent)
+(define-struct: Seq ([actions : (Listof Expression)]) #:transparent)
+(define-struct: App ([operator : Expression]
+                     [operands : (Listof Expression)]) #:transparent)
+
+(: last-exp? ((Listof Expression) -> Boolean))
+(define (last-exp? seq) 
+  (null? (cdr seq)))
+
+(: first-exp ((Listof Expression) -> Expression))
+(define (first-exp seq) (car seq))
+
+(: rest-exps ((Listof Expression) -> (Listof Expression)))
+(define (rest-exps seq) (cdr seq))
\ No newline at end of file
diff --git a/find-toplevel-variables.rkt b/find-toplevel-variables.rkt
index b3217bc..7098444 100644
--- a/find-toplevel-variables.rkt
+++ b/find-toplevel-variables.rkt
@@ -1,5 +1,6 @@
 #lang typed/racket/base
-(require "typed-structs.rkt"
+(require "expression-structs.rkt"
+         "lexical-structs.rkt"
          "helpers.rkt"
          racket/list)
 
diff --git a/typed-structs.rkt b/il-structs.rkt
similarity index 67%
rename from typed-structs.rkt
rename to il-structs.rkt
index fa16cfa..46c7815 100644
--- a/typed-structs.rkt
+++ b/il-structs.rkt
@@ -2,37 +2,6 @@
 (provide (all-defined-out))
 
 
-;; Expressions
-
-(define-type ExpressionCore (U Top Constant Var Branch Def Lam Seq #;App))
-(define-type Expression (U ExpressionCore #;Assign))
-
-(define-struct: Top ([prefix : Prefix]
-                     [code : ExpressionCore]) #:transparent)
-(define-struct: Constant ([v : Any]) #:transparent)
-(define-struct: Var ([id : Symbol]) #:transparent)
-(define-struct: Assign ([variable : Symbol]
-                        [value : Expression]) #:transparent)
-(define-struct: Branch ([predicate : Expression]
-                        [consequent : Expression]
-                        [alternative : Expression]) #:transparent)
-(define-struct: Def ([variable : Symbol] 
-                     [value : Expression]) #:transparent)
-(define-struct: Lam ([parameters : (Listof Symbol)]
-                     [body : Expression]) #:transparent)
-(define-struct: Seq ([actions : (Listof Expression)]) #:transparent)
-(define-struct: App ([operator : Expression]
-                     [operands : (Listof Expression)]) #:transparent)
-
-(: last-exp? ((Listof Expression) -> Boolean))
-(define (last-exp? seq) 
-  (null? (cdr seq)))
-
-(: first-exp ((Listof Expression) -> Expression))
-(define (first-exp seq) (car seq))
-
-(: rest-exps ((Listof Expression) -> (Listof Expression)))
-(define (rest-exps seq) (cdr seq))
 
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -173,27 +142,3 @@
 (define-struct: BasicBlock ([name : Symbol] 
                             [stmts : (Listof UnlabeledStatement)]) #:transparent)
 
-
-;;;;;;;;;;;;;;
-
-;;  Lexical environments
-
-;; A toplevel prefix contains a list of toplevel variables.
-(define-struct: Prefix ([names : (Listof Symbol)])
-  #:transparent)
-
-;; A compile-time environment is a (listof (listof symbol)).
-;; A lexical address is either a 2-tuple (depth pos), or 'not-found.
-(define-type CompileTimeEnvironment (Listof (U (Listof Symbol)
-                                               Prefix)))
-(define-type LexicalAddress (U LocalAddress PrefixAddress))
-
-(define-struct: LocalAddress ([depth : Natural]
-                              [pos : Natural])
-  ;; These need to be treated transparently for equality checking.
-  #:transparent)
-(define-struct: PrefixAddress ([depth : Natural]
-                               [pos : Natural]
-                               [name : Symbol])
-  ;; These need to be treated transparently for equality checking.
-  #:transparent)
\ No newline at end of file
diff --git a/lexical-env.rkt b/lexical-env.rkt
index da44f4f..576728c 100644
--- a/lexical-env.rkt
+++ b/lexical-env.rkt
@@ -1,8 +1,14 @@
 #lang typed/racket/base
 
 (require racket/list
-         "typed-structs.rkt")
-(provide find-variable extend-lexical-environment lexical-environment-pop-depth)
+         "il-structs.rkt"
+         "lexical-structs.rkt"
+         "sets.rkt")
+(provide find-variable 
+         extend-lexical-environment
+         lexical-environment-pop-depth
+         collect-lexical-references
+         lexical-references->compile-time-environment)
 
 
 ;; find-variable: symbol compile-time-environment -> lexical-address
@@ -51,4 +57,49 @@
         [(Prefix? (first cenv))
          1]
         [(list? (first cenv))
-         1]))
\ No newline at end of file
+         1]))
+
+
+
+
+(: collect-lexical-references ((Listof LexicalAddress) 
+                               -> 
+                               (Listof (U EnvLexicalReference EnvWholePrefixReference))))
+;; Given a list of lexical addresses, computes a set of unique references.
+;; Multiple lexical addresses to a single prefix should be treated identically.
+(define (collect-lexical-references addresses)
+  (let: ([prefix-references : (Setof EnvWholePrefixReference) (new-set)]
+         [lexical-references : (Setof EnvLexicalReference) (new-set)])
+        (let: loop : (Listof (U EnvLexicalReference EnvWholePrefixReference)) 
+              ([addresses : (Listof LexicalAddress) addresses])
+              (cond 
+                [(empty? addresses)
+                 (append (set->list prefix-references) (set->list lexical-references))]
+                [else
+                 (let ([addr (first addresses)])
+                   (cond
+                     [(LocalAddress? addr)
+                      (set-insert! lexical-references
+                                   (make-EnvLexicalReference (LocalAddress-depth addr)
+                                                             (LocalAddress-pos addr)))
+                      (loop (rest addresses))]
+                     [(PrefixAddress? addr)
+                      (set-insert! prefix-references
+                                   (make-EnvWholePrefixReference (PrefixAddress-depth addr)))
+                      (loop (rest addresses))]))]))))
+
+
+(: lexical-references->compile-time-environment ((Listof (U EnvLexicalReference EnvWholePrefixReference))
+                                                 CompileTimeEnvironment
+                                                 -> CompileTimeEnvironment))
+(define (lexical-references->compile-time-environment refs cenv)
+  cenv
+  #;(cond
+    [(empty? refs)
+     cenv]
+    [else
+     (let ([a-ref (first refs)])
+       (cond
+         [(EnvLexicalReference? a-ref)
+          ...]))]))
+
diff --git a/lexical-structs.rkt b/lexical-structs.rkt
new file mode 100644
index 0000000..0a4a6cd
--- /dev/null
+++ b/lexical-structs.rkt
@@ -0,0 +1,27 @@
+#lang typed/racket/base
+
+(provide (all-defined-out))
+
+;;;;;;;;;;;;;;
+
+;;  Lexical environments
+
+;; A toplevel prefix contains a list of toplevel variables.
+(define-struct: Prefix ([names : (Listof Symbol)])
+  #:transparent)
+
+;; A compile-time environment is a (listof (listof symbol)).
+;; A lexical address is either a 2-tuple (depth pos), or 'not-found.
+(define-type CompileTimeEnvironment (Listof (U (Listof Symbol)
+                                               Prefix)))
+(define-type LexicalAddress (U LocalAddress PrefixAddress))
+
+(define-struct: LocalAddress ([depth : Natural]
+                              [pos : Natural])
+  ;; These need to be treated transparently for equality checking.
+  #:transparent)
+(define-struct: PrefixAddress ([depth : Natural]
+                               [pos : Natural]
+                               [name : Symbol])
+  ;; These need to be treated transparently for equality checking.
+  #:transparent)
\ No newline at end of file