require "regex"

# This tests whether a pattern matches a string.
match = /p([a-z]+)ch/.match("peach")
puts match

# For other regex tasks, you'll use the Regex class.
r = /p([a-z]+)ch/

# Here's a match test like we saw earlier.
puts r.match("peach")

# This finds the match for the regex.
puts r.match("peach punch").try(&.[0])

# This also finds the first match but returns the
# start and end indexes for the match instead of the
# matching text.
puts "idx: #{r.match("peach punch").try(&.begin)}..#{r.match("peach punch").try(&.end)}"

# The named_captures method includes information about
# both the whole-pattern matches and the captures
# within those matches.
puts r.match("peach punch").try(&.named_captures)

# To find all matches for a regex:
puts "peach punch pinch".scan(r).map(&.[0])

# Providing a limit as the second argument will limit the number
# of matches.
puts "peach punch pinch".scan(r, 2).map(&.[0])

# The regex package can also be used to replace
# subsets of strings with other values.
puts "a peach".gsub(r, "<fruit>")

# The with_index method allows you to transform matched
# text with a given block.
in_bytes = "a peach".bytes
out_bytes = in_bytes.map_with_index do |byte, index|
  if r.match(in_bytes[index..].map(&.chr).join)
    byte.chr.upcase.bytes[0]
  else
    byte
  end
end
puts String.new(out_bytes)