# HG changeset patch
# User J. H. Palmieri <palmieri@math.washington.edu>
# Date 1268545575 28800
# Node ID 245ed8312483f0f1cf1b070f9f3dd5a259cc7b19
# Parent  3510ac19c520e7e58df5a6e267cffb50164d319a
trac 8528: doctests

diff -r 3510ac19c520 -r 245ed8312483 sage/symbolic/expression.pyx
--- a/sage/symbolic/expression.pyx	Sat Mar 13 16:38:21 2010 -0800
+++ b/sage/symbolic/expression.pyx	Sat Mar 13 21:46:15 2010 -0800
@@ -3741,6 +3741,18 @@
             Infinity
             sage: t.n()
             +infinity
+
+        Some expressions can't be evaluated numerically::
+
+            sage: n(sin(x))
+            Traceback (most recent call last):
+            ...
+            TypeError: cannot evaluate symbolic expression numerically
+            sage: a = var('a')
+            sage: (x^2 + 2*x + 2).subs(x=a).n()
+            Traceback (most recent call last):
+            ...
+            TypeError: cannot evaluate symbolic expression numerically
         """
         if prec is None:
             if digits is None: