Set current namespace to the current module. Fixes #208.

The pconvert-lib printer checks the namespace for (pre-)defined symbols.

If the current namespace is not configured, as what would happen during module
instantiation, user-written functions like my-add1 would be printed differently.
This also affects the error message from the check-expects.

    #lang htdp/isl+
    (define (my-add1 n) (+ n 1))
    my-add1
    (check-expect my-add1 2)

Output:

    Welcome to DrRacket.
    (lambda (a1) ...)

    Ran 1 test.
    0 tests passed.

    check-expect ... error ... :: first argument of equality cannot
    be a function, given (lambda (a1) ...)

    > my-add1
    my-add1

htdp-lib/htdp/bsl/runtime.rkt

@@ -1,5 +1,6 @@
 #lang racket/base
 (provide configure configure/settings
+         current-module-namespace-variable-reference
          options->sl-runtime-settings
          (struct-out sl-runtime-settings)
          sl-render-value/format)
@@ -47,6 +48,21 @@
                        (and (memq 'use-function-output-syntax options) #t)
                        (and (memq 'output-function-instead-of-lambda options) #t)))
 
+(define current-module-namespace (make-parameter #f))
+
+;; (parameter/c (or/c #f variable-reference?))
+(define current-module-namespace-variable-reference
+  (make-derived-parameter current-module-namespace
+                          ;; guard
+                          (λ (varref)
+                            (if (variable-reference? varref)
+                                (variable-reference->namespace varref)
+                                #f))
+                          ;; wrap -- cannot retrieve value
+                          (λ (ns)
+                            (raise-user-error 'current-module-namespace-variable-reference
+                                              "parameter is write-only"))))
+
 (define (configure options)
   (configure/settings (options->sl-runtime-settings options)))
 
@@ -80,6 +96,9 @@
           (or (signature-name val)
               '<signature>)]
          [(is-image? val) val]
+         [(current-module-namespace) => (λ (ns)
+                                          (parameterize ([current-namespace ns])
+                                            (ph val basic sub)))]
          [else (ph val basic sub)]))))
   (use-named/undefined-handler
    (lambda (x)

htdp-lib/lang/private/teach-module-begin.rkt

@@ -155,6 +155,10 @@
            #`(#%plain-module-begin
               #,(stepper-syntax-property
                  #`(begin
+                     (#%require (only htdp/bsl/runtime
+                                      current-module-namespace-variable-reference))
+                     (current-module-namespace-variable-reference
+                      (#%variable-reference))
                      (define repl? #f) ; whether we're in the REPL now
                      (let ((handle (uncaught-exception-handler)))
                        (uncaught-exception-handler