Introduction

Boost.Math provides a collection of mathematical constants.

Why use Boost.Math mathematical constants?

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!)
Effortless - avoiding a search of reference sources.
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.
Accurate - ensuring that the values are as accurate as possible for the chosen floating-point type
- No loss of accuracy from repeated rounding of intermediate computations.
- Result is computed with higher precision and only rounded once.
- Less risk of inaccurate result from functions pow, trig and log at corner cases.
- Less risk of cancellation error.
Portable - as possible between different systems using different floating-point precisions: see use in template code.
Tested - by comparison with other published sources, or separately computed at long double precision.
Faster - can avoid (re-)calculation at runtime.
- If the value returned is a builtin type then it's returned by value as a constexpr (C++11 feature, if available).
- 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:
- Functions pow, trig or log are used.
- Inside an inner loop.
- Using a high-precision UDT like Boost.Multiprecision.
- Compiler optimizations possible with built-in types, especially double, are not available.

Boost C++ Libraries

Introduction

Why use Boost.Math mathematical constants?