StringScanner#scan

call-seq: scan(pattern) -> substring or nil

Attempts to match the given pattern at the beginning of the target substring.

If the match succeeds:

• Returns the matched substring.

• Increments the byte position by substring.bytesize, and may increment the character position.

• Sets match values.

scanner = StringScanner.new(HIRAGANA_TEXT)
scanner.string     # => "こんにちは"
scanner.pos = 6
scanner.scan(/に/) # => "に"
put_match_values(scanner)
# Basic match values:
#   matched?:       true
#   matched_size:   3
#   pre_match:      "こん"
#   matched  :      "に"
#   post_match:     "ちは"
# Captured match values:
#   size:           1
#   captures:       []
#   named_captures: {}
#   values_at:      ["に", nil]
#   []:
#     [0]:          "に"
#     [1]:          nil
put_situation(scanner)
# Situation:
#   pos:       9
#   charpos:   3
#   rest:      "ちは"
#   rest_size: 6

If the match fails:

• Returns nil.

• Does not increment byte and character positions.

• Clears match values.

scanner.scan(/nope/)           # => nil
match_values_cleared?(scanner) # => true