fixed error message for sqr

svn: r14515

collects/lang/private/beginner-funs.ss

@@ -44,7 +44,7 @@
 	"to determine the remainder of dividing the first by the second integer (exact or inexact)")
       (modulo (integer integer -> integer)
 	"to find the remainder of the division of the first number by the second; try (modulo 4 3) (modulo 4 -3)") 
-      (sqr (number -> number)
+      ((beginner-sqr sqr) (number -> number)
 	"to compute the square of a number")
       (sqrt (number -> number)
 	"to compute the square root of a number")

collects/lang/private/teachprims.ss

@@ -10,7 +10,8 @@ namespace.
 |#
 (module teachprims mzscheme
 
-  (require mzlib/list
+  (require mzlib/list 
+           mzlib/math
            mzlib/etc)
   
   (define-syntax (define-teach stx)
@@ -142,6 +143,15 @@ namespace.
     (lambda (a b . args)
       (apply * a b args)))
   
+  (define-teach beginner sqr
+    (lambda (a)
+      (unless (number? a)
+        (raise
+	  (make-exn:fail:contract
+	    (format "sqr: expected number; given ~e" a)
+	    (current-continuation-marks))))
+      (sqr a)))
+  
   (define-teach beginner member 
     (lambda (a b)
       (check-second 'member a b)
@@ -312,6 +322,7 @@ namespace.
     beginner-+
     beginner-/
     beginner-*
+    beginner-sqr
     beginner-list?
     beginner-member
     beginner-cons