Returns the position of the last occurrence of a string, needle, in the receiving buffer. It returns 0 if needle is the null string or not found. By default, the search starts at the last character of the receiving buffer and scans backward to the beginning of the string. You can override this by specifying start, the point at which the backward scan starts and length, the range of characters to scan. The start must be a positive whole number and defaults to receiving_buffer~length if larger than that value or omitted. The length must be a non-negative whole number and defaults to start.

See also methods caselessLastPos and pos.

x1 = .mutablebuffer~new("abc def ghi")
x1~lastPos(" ")      -->    8
x1 = .mutablebuffer~new("abcdefghi")
x1~lastPos(" ") --> 0
x1 = .mutablebuffer~new("efgxyz")
x1~lastPos("xy")     -->    4
x1 = .mutablebuffer~new("abc def ghi")
x1~lastPos(" ",7) --> 4