# HG changeset patch
# User Ross Kyprianou <ross7k@gmail.com>
# Date 1273850198 -34200
# Node ID 0d75eeb0ff901b765402811dc9e511ac2f21fdae
# Parent  b052a914e445de73b2fc9c1356606479a917316c
Trac 8983: erf(0) should return 0

diff -r b052a914e445 -r 0d75eeb0ff90 sage/functions/other.py
--- a/sage/functions/other.py
+++ b/sage/functions/other.py
@@ -24,7 +24,6 @@
 one_half = ~SR(2)
 
 class Function_erf(BuiltinFunction):
-    _eval_ = BuiltinFunction._eval_default
     def __init__(self):
         r"""
         The error function, defined as
@@ -39,6 +38,8 @@
             erf(2)
             sage: erf(2).n()
             0.995322265018953
+            sage: erf(0)
+            0.0
             sage: loads(dumps(erf))
             erf
 
@@ -60,6 +61,17 @@
         """
         BuiltinFunction.__init__(self, "erf", latex_name=r"\text{erf}")
 
+    def _eval_(self, x):
+        """
+        EXAMPLES::
+
+            sage: erf(0)
+            0.0
+        """
+        if x.is_zero():
+            return 0.0
+        return BuiltinFunction._eval_default(self, x)
+
     def _evalf_(self, x, parent=None):
         """
         EXAMPLES::