# Computing dilogarithm

I'm measuring the integral of a quantity which, mathematically, requires the computation of a dilogarithm function.

$$\operatorname{Li}_2(be^{ax})$$

where $b$ and $a$ (are real and) can be positive or negative. Dilogarithm has very nice properties that enable us to compute its value efficiently, For $|z|<1$, the following series converges absolutely:

$$\operatorname{Li}_2(z)=\sum_{n=1}^{\infty}\frac{z^n}{n^2}$$

I'm wondering is there any explicit way to compute or numerically approximate dilogarithm -- especially in COMSOL?