The data type index refers to a specified sequence of list element indexes. A list index sequence may be specified in one of the following forms.

value / form	description
true	All index positions of the list [0:size-1]
false	No index positions
"all"	All index positions of the list [0:size-1]
"none"	No index positions
"rands"	Random index selection of the list [0:size-1]
"even"	The even index of the list [0:size-1]
"odd"	The odd index of the list [0:size-1]
<integer>	The single position given by an <integer>
<range>	The range of positions given by a <range>
<integer-list>	The list of positions give in <integer-list>

The function index_gen() can be used to convert a value of this data type into a sequence of list element indexes.

Example

// list
l1 = [a,b,c,d,e,f]
 
// index sequence
index_gen(l1)          = [0,1,2,3,4,5]
index_gen(l1, "rands") = [0,2,5]