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Manipulating Variable Argument Lists

    Three functions are available for manipulating variable argument lists.   The first is num_args(...), which returns the number of arguments with which it was invoked, first expanding any ... ellipsis arguments.   The second is nth_arg(n, ...), which returns its n'th argument, numbering n itself as 0.   The third is missing( ), which returns a vector with T in each element that corresponds to a missing parameter and F elsewhere.

See § 6.4.4 and § 6.5, for a full discussion of these functions.    

Thu Nov 13 16:44:05 EST 1997