A function added by the New Vegas Script Extender.
Returns the previous key of an array, after that specified. For regular arrays (list arrays) this is just equivalent to (SpecifiedKey - 1). This function is most useful for map and stringmap arrays, where keys are dynamic. Note that map and stringmap arrays are always sorted in ascending numeric or alphanumeric order, regardless of the order of element insertion.
(key:int-or-float-or-string) Ar_Prev Source:array Next:key
array_var MyMap int iKey ; * or float/string_var as appropriate for array let iKey := Ar_Last MyMap ; * get last element while iKey != Ar_BadNumericIndex ; do something for every valid key in array, in reverse order let iKey := Ar_Prev MyMap, iKey loop