ruby/doc/strscan/methods/set_pos.md

call-seq: pos = n -> n pointer = n -> n

Sets the [byte position][2] and the [character position][11]; returns n.

Does not affect [match values][9].

For non-negative n, sets the position to n:

scanner = StringScanner.new(HIRAGANA_TEXT)
scanner.string  # => "こんにちは"
scanner.pos = 3 # => 3
scanner.rest    # => "んにちは"
scanner.charpos # => 1

For negative n, counts from the end of the [stored string][1]:

scanner.pos = -9 # => -9
scanner.pos      # => 6
scanner.rest     # => "にちは"
scanner.charpos  # => 2