unclear function /how dose it work.

[axa643]

double b_fn(double a, double t)
{
return (a == 0.0) ? t : (1.0 - std::exp(-a * t)) / a;
}


// please i need to know what dose and how this function dose, work? i can not understand any thing starting from return till then end.

Thank you for the help in advanced.

[helios]

If a is zero, b_fn() returns t. If a is non-zero, b_fn() returns 1 - e^{-a t} / a, where e is Euler's number.

[axa643]

thank you very much helios(13344).

[helios]

Correction: If a is non-zero, b_fn() returns (1 - e^{-a t}) / a.

[48T7M4Gy]

http://en.cppreference.com/w/cpp/numeric/math/exp