You can include several functions in your dice expressions:
Roll a d20, divide by two, and round the result to the nearest whole number.
Many tabletop games have specific rounding rules, check the Rounding Functions
section for a comprehensive list of rounding options that are supported.
Roll 2d20 and 4d10, returning the sum of whichever dice pool rolled the smallest number. This function can compare an arbitrary number of parameters.
Roll 2d20 and 4d10, returning the sum of whichever dice pool rolled the largest number. This function can compare an arbitrary number of parameters.
clamp(d20+d4, 5, 15)
Roll a d20 and a d4, and clamp the result so it is never less than 5, or greater than 15.
Return a random number from 1 to 20 without rolling any dice.
There are other mathematical functions, less common for use with dice but available to you if you want them: sin(), cos(), tan(), asin(), acos(), atan(), atan2(,), tanh(), exp(), sqrt(), ln(), abs(), pow(,), lerp(,,), mod(,), sign().