Make atan2(0,0) return undef

p4raw-id: //depot/perl@33676

diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index 3a0d103..f17311a 100644 (file)
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -492,8 +492,7 @@ function, or use the familiar relation:
 
     sub tan { sin($_[0]) / cos($_[0])  }
 
-Note that atan2(0, 0) is not well-defined, however the Perl
-implmentation returns C<0> for this value.
+Perl returns C<undef> for C<atan(0,0)>.
 
 =item bind SOCKET,NAME
 X<bind>

diff --git a/pp.c b/pp.c
index d940d10..145e74c 100644 (file)
--- a/pp.c
+++ b/pp.c
@@ -2798,7 +2798,10 @@ PP(pp_atan2)
     dVAR; dSP; dTARGET; tryAMAGICbin(atan2,0);
     {
       dPOPTOPnnrl;
-      SETn(Perl_atan2(left, right));
+      if (left == 0.0 && right == 0.0)
+         SETs(&PL_sv_undef);
+      else
+         SETn(Perl_atan2(left, right));
       RETURN;
     }
 }

diff --git a/t/op/exp.t b/t/op/exp.t
index 9bc44b4..c49a34b 100755 (executable)
--- a/t/op/exp.t
+++ b/t/op/exp.t
@@ -6,7 +6,7 @@ BEGIN {
     require './test.pl';
 }
 
-plan tests => 16;
+plan tests => 17;
 
 # compile time evaluation
 
@@ -57,3 +57,7 @@ cmp_ok(round(cos(-1 * $pi_2)), '==', 0.0);
 # atan2() tests were removed due to differing results from calls to
 # atan2() on various OS's and architectures.  See perlport.pod for
 # more information.
+
+# Just test that atan2(0,0) is undef, because that's implemented
+# from within perl.
+ok(!defined(atan2(0,0)), 'atan2(0,0) returns undef');