Attempt to interpret a function given the arguments.
Input:
istate state for calling function (NULL if none)
arguments function arguments
thisarg 'this', if a needThis() function, NULL if not.
Return result expression if successful, TOKcantexp if not,
or CTFEExp if function returned void.
Attempt to interpret a function given the arguments. Input: istate state for calling function (NULL if none) arguments function arguments thisarg 'this', if a needThis() function, NULL if not.
Return result expression if successful, TOKcantexp if not, or CTFEExp if function returned void.