The parser understands the following functions f(a):
abs(a) sin(a) cos(a)
tan(a) ln(a) log(a)
int(a) frac(a)
asin(a) acos(a) atan(a)
sinh(a) cosh(a) tanh(a)
asinh (a)
acosh(a) atanh(a) ceil(a)
floor(a) round(a) exp(a)
sqr(a)
sqrt(a) sign(a) step(a)
random(a)