From 1a1c1feabce36a91bedbb21eee4019e5977833ab Mon Sep 17 00:00:00 2001
From: Robby Findler <robby@racket-lang.org>
Date: Sat, 29 Jun 2013 00:48:15 -0500
Subject: [PATCH] adjust htdp so missing teachpacks just print error messages
 and continue, rather than raising exceptions

---
 pkgs/drracket/drracket/private/main.rkt | 11 ++---------
 pkgs/htdp/lang/run-teaching-program.rkt | 16 ++++++++++------
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/pkgs/drracket/drracket/private/main.rkt b/pkgs/drracket/drracket/private/main.rkt
index 7b72b207c7..f4c1d04a36 100644
--- a/pkgs/drracket/drracket/private/main.rkt
+++ b/pkgs/drracket/drracket/private/main.rkt
@@ -109,15 +109,8 @@
                              (memq (cdr x) '(left top top-no-label right)))))
 
 (drr:set-default 'drracket:htdp:last-set-teachpacks
-                         '() 
-                         (λ (x)
-                           (and (list? x)
-                                (andmap (λ (x)
-                                          (and (list? x)
-                                               (pair? x)
-                                               (eq? (car x) 'lib)
-                                               (andmap string? (cdr x))))
-                                        x))))
+                 '() 
+                 (listof (cons/c 'lib (listof string?))))
 (drr:set-default 'drracket:defs/ints-horizontal #f boolean?)
 
 (drr:set-default 'drracket:child-only-memory-limit (* 1024 1024 128)
diff --git a/pkgs/htdp/lang/run-teaching-program.rkt b/pkgs/htdp/lang/run-teaching-program.rkt
index 4f5983a3af..b33176a7ef 100644
--- a/pkgs/htdp/lang/run-teaching-program.rkt
+++ b/pkgs/htdp/lang/run-teaching-program.rkt
@@ -98,12 +98,16 @@
 ;; syntax objects that require them (tagged
 ;; with stepper-skip-completely)
 (define (teachpacks->requires teachpacks)
-  (for/list ([tp (in-list teachpacks)])
-    (unless (file-exists? (build-path (apply collection-path (cddr tp))
-                                      (cadr tp)))
-      (error 'teachpack (missing-tp-message tp)))
-    (stepper-skip
-     (datum->syntax #f `(require ,tp)))))
+  (filter
+   values
+   (for/list ([tp (in-list teachpacks)])
+     (cond
+       [(file-exists? (build-path (apply collection-path (cddr tp))
+                                  (cadr tp)))
+        (stepper-skip
+         (datum->syntax #f `(require ,tp)))]
+       [else
+        (eprintf "~a\n" (missing-tp-message tp))]))))
 
 (define (missing-tp-message x)
   (let* ([m (regexp-match #rx"/([^/]*)$" (cadr x))]