Math: debug output for Half with proper amount of decimal places.

The totally random places after were not exactly useful. This file was
sitting here for a while, not sure why I didn't commit that earlier.

src/Magnum/CMakeLists.txt

@@ -133,6 +133,7 @@ endif()
 # Files shared between main library and math unit test library
 set(MagnumMath_SRCS
     Math/Color.cpp
+    Math/Half.cpp
     Math/Functions.cpp
     Math/Packing.cpp
     Math/instantiation.cpp)

src/Magnum/Math/Half.cpp

@@ -0,0 +1,41 @@
+/*
+    This file is part of Magnum.
+
+    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018
+              Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+#include "Magnum/Math/Half.h"
+
+#include <iomanip>
+#include <sstream>
+
+namespace Magnum { namespace Math {
+
+Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, Half value) {
+    std::ostringstream out;
+    /* Wikipedia says it's 3 or 4 decimal places:
+       https://en.wikipedia.org/wiki/Half-precision_floating-point_format */
+    out << std::setprecision(4) << Float(value);
+    return debug << out.str();
+}
+
+}}

src/Magnum/Math/Half.h

@@ -150,10 +150,16 @@ inline Half operator "" _h(long double value) { return Half(Float(value)); }
 
 }
 
-/** @debugoperator{Half} */
-inline Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, Half value) {
-    return debug << Float(value);
-}
+/**
+@debugoperator{Half}
+
+Prints the value with 4 significant digits.
+@see @ref Corrade::Utility::Debug::operator<<(float),
+    @ref Corrade::Utility::Debug::operator<<(double),
+    @ref Corrade::Utility::Debug::operator<<(long double value)
+@todoc remove `long double value` once doxygen can link to long double overloads properly
+*/
+MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, Half value);
 
 }}
 

src/Magnum/Math/Test/HalfTest.cpp

@@ -609,12 +609,12 @@ void HalfTest::debug() {
 
     std::ostringstream out;
 
-    Debug{&out} << -3.64_h << Half{Constants::inf()}
+    Debug{&out} << -36.41_h << Half{Constants::inf()}
         << Math::Vector3<Half>{3.14159_h, -1.4142_h, 1.618_h};
     #ifdef _MSC_VER
-    CORRADE_COMPARE(out.str(), "-3.64063 inf Vector(3.14063, -1.41406, 1.61816)\n");
+    CORRADE_COMPARE(out.str(), "-36.41 inf Vector(3.141, -1.414, 1.618)\n");
     #else
-    CORRADE_COMPARE(out.str(), "-3.64062 inf Vector(3.14062, -1.41406, 1.61816)\n");
+    CORRADE_COMPARE(out.str(), "-36.41 inf Vector(3.141, -1.414, 1.618)\n");
     #endif
 }