String matching

# title: String matching
# source: https://rosettacode.org/wiki/String_matching
# category: Rosetta Code
# difficulty: Intro
# summary: Find every starting index of a pattern inside a fixed string with a naive scan.
# tags: popular, strings, search, loops
# vibe: 0.2

def matches_at?(text, pattern, start_index)
  offset = 0

  while offset < pattern.length
    if text.slice(start_index + offset) != pattern.slice(offset)
      return false
    end
    offset = offset + 1
  end

  true
end

def string_matching(text, pattern)
  matches = []
  index = 0

  while index + pattern.length <= text.length
    if matches_at?(text, pattern, index)
      matches = matches.push(index)
    end
    index = index + 1
  end

  matches
end

def run
  {
    aba_in_ababa: string_matching("ababa", "aba"),
    ana_in_bananas: string_matching("bananas", "ana")
  }
end