Boost.Math provides a collection of mathematical constants.
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Readable. For the very many jobs just using built-in like double, you can just write expressions like
double area = pi * r * r;
(If that's all you want, jump direct to use
in non-template code!)
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Effortless - avoiding a search of reference sources.
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Usable with both builtin floating point types, and user-defined, possibly
extended precision, types such as NTL, MPFR/GMP, mp_float: in the latter
case the constants are computed to the necessary precision and then cached.
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Accurate - ensuring that the values are as accurate as possible for the
chosen floating-point type
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No loss of accuracy from repeated rounding of intermediate computations.
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Result is computed with higher precision and only rounded once.
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Less risk of inaccurate result from functions pow, trig and log at
corner cases.
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Less risk of cancellation
error.
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Portable - as possible between different systems using different floating-point
precisions: see use in template
code.
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Tested - by comparison with other published sources, or separately computed
at long double precision.
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Faster - can avoid (re-)calculation at runtime.
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If the value returned is a builtin type then it's returned by value
as a
constexpr (C++11
feature, if available).
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If the value is computed and cached (or constructed from a string
representation and cached), then it's returned by constant reference.
This can be significant if:
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Functions pow, trig or log are used.
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Inside an inner loop.
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Using a high-precision UDT like Boost.Multiprecision.
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Compiler optimizations possible with built-in types, especially
double, are not available.
