CODEWITHSUNDEEP
rubyregexoverlap
sschmeck
sschmeck

Reputation: 7705

Find overlapping Regexp matches

I want to find all matches within a given string including overlapping matches. How could I achieve it?

# Example
"a-b-c-d".???(/\w-\w/)  # => ["a-b", "b-c", "c-d"] expected

# Solution without overlapped results
"a-b-c-d".scan(/\w-\w/) # => ["a-b", "c-d"], but "b-c" is missing

Upvotes: 13

Views: 1487

Answers (2)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627086

Use capturing inside a positive lookahead:

"a-b-c-d".scan(/(?=(\w-\w))/).flatten
 # => ["a-b", "b-c", "c-d"]

See Ruby demo

Upvotes: 16

Cary Swoveland
Cary Swoveland

Reputation: 110725

I suggest a non-regex solution:

"a-b-c-d".delete('-').each_char.each_cons(2).map { |s| s.join('-') }
  #=> ["a-b", "b-c", "c-d"]

or

"a-b-c-d".each_char.each_cons(3).select.with_index { |_,i| i.even? }.map(&:join)
  #=> ["a-b", "b-c", "c-d"]

or

enum = "a-b-c-d".each_char
a = []
loop do
  a << "%s%s%s" % [enum.next, enum.next, enum.peek]
end
a #=> ["a-b", "b-c", "c-d"]

Upvotes: 4

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