FUNCTIONS

 PPL allows functions, returning the specified type, with the specified
 arguments to be used in an expression.  Some functions require no
 arguments, if arguments are required, the arguments may all be expressions
 of any type, but will be converted to one of the following types prior to
 function evaluation

    BEXP (BOOLEAN)
    DEXP (DATE)
    IEXP (INTEGER)
    MEXP (MONEY)
    SEXP (STRING)
    TEXP (TIME))