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125 lines
3.8 KiB
Plaintext
125 lines
3.8 KiB
Plaintext
[section:fpclass Floating-Point Classification: Infinities and NaNs]
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[h4 Synopsis]
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#define FP_ZERO /* implementation specific value */
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#define FP_NORMAL /* implementation specific value */
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#define FP_INFINITE /* implementation specific value */
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#define FP_NAN /* implementation specific value */
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#define FP_SUBNORMAL /* implementation specific value */
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template <class T>
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int fpclassify(T t);
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template <class T>
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bool isfinite(T z); // Neither infinity nor NaN.
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template <class T>
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bool isinf(T t); // Infinity (+ or -).
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template <class T>
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bool isnan(T t); // NaN.
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template <class T>
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bool isnormal(T t); // isfinite and not denormalised.
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#include <boost\math\special_functions\fpclassify.hpp>
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to use these functions.
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[h4 Description]
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These functions provide the same functionality as the macros with the same
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name in C99, indeed if the C99 macros are available, then these functions
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are implemented in terms of them, otherwise they rely on `std::numeric_limits<>`
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to function.
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Note that the definition of these functions
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['does not suppress the definition of these names as macros by math.h]
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on those platforms that already provide
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these as macros. That mean that the following have differing meanings:
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using namespace boost::math;
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// This might call a global macro if defined,
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// but might not work if the type of z is unsupported
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// by the std lib macro:
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isnan(z);
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//
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// This calls the Boost version
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// (found via the "using namespace boost::math" declaration)
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// it works for any type that has numeric_limits support for type z:
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(isnan)(z);
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//
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// As above but with explicit namespace qualification.
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(boost::math::isnan)(z);
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//
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// This will cause a compiler error if isnan is a native macro:
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boost::math::isnan(z);
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// So always use instead:
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(boost::math::isnan)(z);
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//
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// You can also add a using statement,
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// globally to a .cpp file, or to a local function in a .hpp file.
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using boost::math::isnan;
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// so you can write the shorter and less cluttered
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(isnan)(z)
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// But, as above, if isnan is a native macro, this causes a compiler error,
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// because the macro always 'gets' the name first, unless enclosed in () brackets.
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Detailed descriptions for each of these functions follows:
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template <class T>
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int fpclassify(T t);
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Returns an integer value that classifies the value /t/:
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[table
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[[fpclassify value] [class of t.]]
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[[FP_ZERO] [If /t/ is zero.]]
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[[FP_NORMAL] [If /t/ is a non-zero, non-denormalised finite value.]]
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[[FP_INFINITE] [If /t/ is plus or minus infinity.]]
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[[FP_NAN] [If /t/ is a NaN.]]
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[[FP_SUBNORMAL] [If /t/ is a denormalised number.]]
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]
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template <class T>
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bool isfinite(T z);
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Returns true only if /z/ is not an infinity or a NaN.
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template <class T>
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bool isinf(T t);
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Returns true only if /z/ is plus or minus infinity.
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template <class T>
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bool isnan(T t);
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Returns true only if /z/ is a [@http://en.wikipedia.org/wiki/NaN NaN].
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template <class T>
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bool isnormal(T t);
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Returns true only if /z/ is a normal number (not zero, infinite, NaN, or denormalised).
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[h5 Floating-point format]
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If you wish to find details of the floating-point format for any particular processor,
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there is a program
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[@../../example/inspect_fp.cpp inspect_fp.cpp]
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by Johan Rade which can be used to print out the processor type,
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endianness, and detailed bit layout of a selection of floating-point values,
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including infinity and NaNs.
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[endsect] [/section:fpclass Floating Point Classification: Infinities and NaNs]
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[/
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Copyright 2006, 2008, 2011 John Maddock, Johan Rade and Paul A. Bristow.
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt).
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]
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