Return nonzero if 'arg' is a function pointer and zero (0) otherwise.
Function pointers are variables of type 'function' as indicated in the
documentation for the type 'function', for example:
f = (: obj, func :);
The return value indicates the type of function pointer using the val‐
ues given in the driver include file "include/function.h".
function pointer type value
--------------------- -----
call_other FP_CALL_OTHER
lfun FP_LOCAL
efun FP_EFUN
simul_efun FP_SIMUL
functional FP_FUNCTIONAL
In addition, the following values will be added in some cases:
FP_HAS_ARGUMENTS arguments provided
FP_OWNER_DESTED creator has been dested
FP_NOT_BINDABLE not rebindable)
The last set of values are bit values and can be tested with bit opera‐
tions. The value FP_MASK is provided for ignoring the bit values and
testing the basic type of the function pointer.
Examples:
To test if a function variable is an efun pointer:
if ((functionp(f) & FP_MASK) == FP_EFUN) ...
to test if it has args:
if (functionp(f) & FP_HAS_ARGUMENTS) ...