ListOffsetBefore

Type

operator

Summary

Find the first or last occurrence of Needle within the head of Haystack Target:An expression which evaluates to a List.

Syntax

the ( first | last ) offset of <Needle> before <Before> in <Haystack>

Description

Use the offset of… before to find where a particular sub-list occurs within a list. Haystack is scanned for a sequence of elements that are equal to the elements of Needle, stopping before the position Before, and the position of the start of the sequence found is returned. If no sub-list of Haystack before the position Before is equal to Needle, the return value is 0. If neither "first" nor "last" is specified, the last matching subsequence is found.

Parameters

Name	Type	Description
Needle		An expression which evaluates to List.
Before		An expression which evaluates to a valid index in Target.

Examples

variable tVar as List
variable tOffset as Number
put ["a", "b", "c", "d", "b","c"]
put the offset of ["b","c"] before 5 in tVar into tOffset
--tOffset contains 2

put the first offset of ["b","c"] before 6 in tVar into tOffset
--tOffset contains 2

Value

Name	Type	Description
return		Returns the index in Haystack.