[builtins] Make sure the Math functions and constants agree.

test/unittests/base/ieee754-unittest.cc

Index: test/unittests/base/ieee754-unittest.cc
diff --git a/test/unittests/base/ieee754-unittest.cc b/test/unittests/base/ieee754-unittest.cc
index c0a1887b5519a00c9e42f80b486e32817aaa60fe..23cf27912e1e40bfb13431779675743efa51e594 100644
--- a/test/unittests/base/ieee754-unittest.cc
+++ b/test/unittests/base/ieee754-unittest.cc
@@ -131,7 +131,7 @@ TEST(Ieee754, Exp) {
   EXPECT_EQ(1.0, exp(2.2250738585072014e-308));
   EXPECT_GE(exp(1.0), exp(0.9999999999999999));
   EXPECT_LE(exp(1.0), exp(1.0000000000000002));

[Raymond Toy, 2016/06/21 16:20:12]

I remember now what the tests in 132 and 133 are doing.  0.999999... is the
largest FP number < 1.  1.000...2 is the smallest FP number > 1.  These two
tests verify that exp(x) is monotonic at 1.

[Benedikt Meurer, 2016/06/22 03:55:59]

Acknowledged.

-  EXPECT_EQ(2.7182818284590455, exp(1.0));

[Raymond Toy, 2016/06/21 16:20:12]

Is it possible to use the constant E here, like you did in the implementation of
exp(x)?

[Benedikt Meurer, 2016/06/22 03:55:59]

Done.

+  EXPECT_EQ(2.718281828459045, exp(1.0));
   EXPECT_EQ(7.38905609893065e0, exp(2.0));
   EXPECT_EQ(1.7976931348622732e308, exp(7.09782712893383973096e+02));
   EXPECT_EQ(2.6881171418161356e+43, exp(100.0));