TODO.txt

Implemented Duals:
- add
- sub
- mul
- div
- sin
- sec
- cos
- csc
- tan
- cot
- exp
- log
- pow
- abs
- asin
- acos
- atan
- sqrt
- sinh
- cosh
- tanh
- gamma
- digamma
- airyAi
- airyBi
- Chi
- Shi
- Ci
- Si
- Ei
- erf
- dilog

Todo:
- hurwitz, riemann zeta
- hypergeo: 1f1, 1f2, 2f1, 3f0
- struve: l0, l1

by the rule:

Γ'(f(x)) = f'(x)Γ(f(x))ψ(f(x)):
Γ(a+bε) = Γ(a) + Γ(a)ψ(a)bε