Document the unportability of atan2() edge cases

and remove unportable tests (by Steve Peters)

p4raw-id: //depot/perl@24388

2 files changed, 15 insertions, 8 deletions

diff --git a/pod/perlport.pod b/pod/perlport.pod
index 863f84d81d..f4e6ddf06f 100644
--- a/pod/perlport.pod
+++ b/pod/perlport.pod
@@ -1540,6 +1540,17 @@ suffixes.  C<-S> is meaningless.  (Win32)
 C<-x> (or C<-X>) determine if a file has an executable file type.
 (S<RISC OS>)
 
+=item atan2 Y,X
+
+Due to issues with various CPUs, math libraries, compilers, and standards,
+results for C<atan2()> may vary depending on any combination of the above.
+Perl attempts to conform to the Open Group/IEEE standards for the results
+returned from C<atan2()>, but cannot force the issue if the system Perl is
+run on does not allow it.  (Tru64, HP-UX 10.20) 
+
+The current version of the standards for C<atan2()> is available at 
+L<http://www.opengroup.org/onlinepubs/009695399/functions/atan2.html>.
+
 =item binmode FILEHANDLE
 
 Meaningless.  (S<Mac OS>, S<RISC OS>)
diff --git a/t/op/exp.t b/t/op/exp.t
index 707deb98a9..9bc44b49b4 100755
--- a/t/op/exp.t
+++ b/t/op/exp.t
@@ -6,7 +6,7 @@ BEGIN {
     require './test.pl';
 }
 
-plan tests => 22;
+plan tests => 16;
 
 # compile time evaluation
 
@@ -54,10 +54,6 @@ cmp_ok(round(cos(-1 * $pi)), '==', -1.0);
 cmp_ok(round(cos($pi_2)), '==', 0.0);
 cmp_ok(round(cos(-1 * $pi_2)), '==', 0.0);
 
-# atan2() tests
-cmp_ok(round(atan2(-0.0, 0.0)), '==', 0);
-cmp_ok(round(atan2(0.0, 0.0)), '==', 0);
-cmp_ok(round(atan2(-0.0, -0.0)), '==', round(-1 * $pi));
-cmp_ok(round(atan2(0.0, -0.0)), '==', round($pi));
-cmp_ok(round(atan2(-1.0, 0.0)), '==', round(-1 * $pi_2));
-cmp_ok(round(atan2(1.0, 0.0)), '==', round($pi_2));
+# atan2() tests were removed due to differing results from calls to
+# atan2() on various OS's and architectures.  See perlport.pod for
+# more information.