diff --git a/.gitignore b/.gitignore
index a1f33d6..f223cee 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,6 @@
 compiled
-doc
\ No newline at end of file
+doc
+*.bak
+*.css
+*.js
+*.html
diff --git a/sicp-doc/sicp.scrbl b/sicp-doc/sicp.scrbl
index 61cba28..79eb4bf 100644
--- a/sicp-doc/sicp.scrbl
+++ b/sicp-doc/sicp.scrbl
@@ -3,7 +3,7 @@
 @(require scribble/manual scribble/eval
           (for-label (except-in sicp #%app #%datum #%top true false identity error)
                      (only-in racket require true false identity error
-                                     natural-number/c any/c)))
+                                     natural-number/c any/c any namespace?)))
 
 @title{SICP Language}
 @defmodule[sicp #:lang]
@@ -67,4 +67,12 @@ then use @racket[#%require].
   The amb operator.
 }
 
+@defproc[(apply-in-underlying-scheme [proc procedure?] [args list?]) any]{
+  An alias for @racket[(apply proc args)].
+}
+
+@defthing[user-initial-environment namespace?]{
+  The current namespace.
+}
+
 Additionally, @racket[true], @racket[false], @racket[identity], and @racket[error] are provided from Racket.
diff --git a/sicp/main.rkt b/sicp/main.rkt
index 5548679..c3a441f 100644
--- a/sicp/main.rkt
+++ b/sicp/main.rkt
@@ -2,11 +2,12 @@
 
 (require racket/provide
          (prefix-in r5rs: r5rs)
-         (rename-in racket [random racket:random]))
+         (only-in racket [random racket:random]))
 
 (provide (filtered-out (λ (name) (regexp-replace #px"^r5rs:" name ""))
-                       (except-out (all-from-out r5rs) r5rs:#%module-begin))
-         (rename-out [module-begin #%module-begin]))
+                       (except-out (all-from-out r5rs) r5rs:#%module-begin r5rs:set!))
+         (rename-out [module-begin #%module-begin]
+                     [amb-set! set!]))
 
 (define-syntax (define+provide stx)
   (syntax-case stx ()
@@ -38,10 +39,12 @@
   (syntax-rules ()
     [(_ A B) (r5rs:cons A (r5rs:delay B))]))
 
+(define+provide apply-in-underlying-scheme r5rs:apply)
 
 (provide amb)
 
-(define (amb-fail) (error "amb tree exhausted"))
+(define (base-amb-fail) (error "amb tree exhausted"))
+(define amb-fail base-amb-fail)
 (define (set-amb-fail! x) (set! amb-fail x))
 
 (define-syntax-rule (explore +prev-amb-fail +sk alt)
@@ -60,6 +63,21 @@
        (explore +prev-amb-fail +sk alt) ...
        (+prev-amb-fail)))))
 
+(define-syntax-rule (amb-set! var val)
+  (if (eq? amb-fail base-amb-fail)
+      (r5rs:set! var val)
+      (let ([+prev-amb-fail amb-fail]
+            [old-value var])
+        (set-amb-fail!
+         (thunk
+          (r5rs:set! var old-value)
+          (+prev-amb-fail)))
+        (r5rs:set! var val))))
+
+(define+provide user-initial-environment #f)
+(define (set-user-initial-environment! namespace)
+  (set! user-initial-environment namespace))
+
 (define-syntax module-begin
   (syntax-rules ()
     ((_ . forms)
@@ -68,4 +86,6 @@
         (print-as-expression #f)
         (print-pair-curly-braces  #t)
         (print-mpair-curly-braces #f))
+      (define-namespace-anchor tmp)
+      (set-user-initial-environment! (namespace-anchor->namespace tmp))
       . forms))))