viafunc() takes 4 arguments: (tabname, colname, type, length) and returns TRUE or FALSE

sortfunc() takes 2 array arguments: (COPYOF ar1, COPYOF arr2) DEFINEd same as each row of the array to be sorted and returns -1 or 0 or +1 meaning less than, equal to, or greater than respectively.

filterfunc() takes a string argument and returns a row of column values (for inserting into a table)