Defines a function that depends on one variable only, which can be of two kinds: interpolatedFromFile or expression. For example, OAFunc are used in MonteCarlo Interactions to define interactions cross sections.
<OAFunc mysp>
kind = interpolatedFromFile
filename = h2StoppingPower.dat
# set bounds of the function from min and max x values in the file.
# option specific to kind = interpolatedFromFile
# setMinMaxFromFile = 1
# f has to be >0.
fmin = 0.
</OAFunc>