Be (somewhat more) consistent about the value of pi

Use M_PI (and friends), where possible, in favor of hand-coded
approximations of various (in)accuracies.  Where that's not available
(e.g. fragment shaders), use the same value that qmath.h uses for
M_PI, for consistency.  Replaced math.h with qmath.h in places that
defined a fall-back in case math.h omits it (it's not in the C++
standard, although M_PI is in POSIX); or removed this entirely where
it wasn't used.

Reworked some code to reduce the amount of arithmetic needed, in the
process; e.g. pulling common factors out of loops.  Revised an
example's doc to not waste time talking about using a six-sig-fig
value for pi (which we no longer do) - it really wasn't relevant, or
anything to be proud of; nor did the doc mention its later use.

Task-number: QTBUG-58083
Change-Id: I5a31e3a2b6a823b97a43209bed61a37b9aa6c05f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/corelib/doc/snippets/code/doc_src_qpair.cpp b/src/corelib/doc/snippets/code/doc_src_qpair.cpp
index f94e3b0d37..e62f91830c 100644
--- a/src/corelib/doc/snippets/code/doc_src_qpair.cpp
+++ b/src/corelib/doc/snippets/code/doc_src_qpair.cpp
@@ -47,6 +47,7 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
+#include <qmath.h>
 
 //! [0]
 QPair<QString, double> pair;
@@ -55,7 +56,7 @@ QPair<QString, double> pair;
 
 //! [1]
 pair.first = "pi";
-pair.second = 3.14159265358979323846;
+pair.second = M_PI;
 //! [1]
 
 //! [struct]
@@ -65,10 +66,10 @@ struct Variable {
 };
 Variable v;
 v.name = "pi";
-v.value = 3.14159265358979323846;
+v.value = M_PI;
 //! [struct]
 
 //! [2]
 QList<QPair<int, double> > list;
-list.append(qMakePair(66, 3.14159));
+list.append(qMakePair(66, M_PI));
 //! [2]