# String mangling **URL:** \ **Category:** Ruby\ **Created:** [December 14, 2005, 1:20pm UTC](https://www.ruby-forum.com/t/string-mangling/50243 "2005-12-14T13:20:48Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 14, 2005, 1:20pm UTC](https://www.ruby-forum.com/t/string-mangling/50243/1 "2005-12-14T13:20:48Z")
Imagine an input string aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee… I have regexp for the parts a,b,c and e can be considered as else. So how can I efficiently search/step through the string from left to right, while calling for each section the fitting handler, kind of case section /aaaa/ … /bbb/ … /cccc/ … else end Thanks for ideas! Martin ---
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 14, 2005, 1:35pm UTC](https://www.ruby-forum.com/t/string-mangling/50243/2 "2005-12-14T13:35:51Z")
On 12/14/05, Martin P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Imagine an input string > aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee… > > I have regexp for the parts a,b,c > and e can be considered as else. > > So how can I efficiently search/step through the string from left to > right, while calling for each section the fitting handler, kind of irb(main):001:0\> s = ‘aaaaabbccccceeebbbbbbbbbbeaaabaacccceee’ =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceee” irb(main):002:0\> s.scan(/(a+)|(b+)|(c+)|([^abc]+)/) =\> [[“aaaaa”, nil, nil, nil], [nil, “bb”, nil, nil], [nil, nil, “ccccc”, nil], [nil, nil, nil, “eee”], [nil, “bbbbbbbbbb”, nil, nil], [nil, nil, nil, “e”], [“aaa”, nil, nil, nil], [nil, “b”, nil, nil], [“aa”, nil, nil, nil], [nil, nil, “cccc”, nil], [nil, nil, nil, “eee”]] irb(main):003:0\> ---
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 14, 2005, 2:14pm UTC](https://www.ruby-forum.com/t/string-mangling/50243/3 "2005-12-14T14:14:57Z")
Martin P. wrote: > /aaaa/ … > > /bbb/ … > > /cccc/ … > > else > > end You are pretty close: > > s=‘aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee’ > > =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee” > > > s.scan /a+|b+|c+/ do |m| > > ?\> case m > > > ``` > > when /a+/ > > puts "A" > > when /b+/ > > puts "B" > > when /c+/ > > puts "C" > > > > ``` > > > > end > > end > > A > > B > > C > > B > > A > > B > > A > > C > > =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee” Or, if you want to avoid a second match: > > s.scan /(a+)|(b+)|(c+)/ do |m| > > ?\> case ( m.inject(0) {|i,e| break i if e; i + 1} ) > > > ``` > > when 0 > > puts "A" > > when 1 > > puts "B" > > when 2 > > puts "C" > > > > ``` > > > > end > > end > > A > > B > > C > > B > > A > > B > > A > > C > > =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee” > > > Kind regards ``` robert ``` ---
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 14, 2005, 2:14pm UTC](https://www.ruby-forum.com/t/string-mangling/50243/4 "2005-12-14T14:14:58Z")
Martin P. wrote: > Imagine an input string > aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee… > > I have regexp for the parts a,b,c > and e can be considered as else. > > So how can I efficiently search/step through the string from left to > right, while calling for each section the fitting handler, kind of You could use String#scan to find bits that find sections that match any of your requirements, then check to see which matched (your patterns could be more complicated, but still distinguishable from one another) str = ‘aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee’ a\_rx = /a+/ b\_rx = /b+/ c\_rx = /c+/ str.scan(/(?:#{a\_rx}|#{b\_rx}|#{c\_rx})/) do | part | case part when a\_rx # … when b\_rx # … when c\_rx # … end end ---
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 14, 2005, 2:39pm UTC](https://www.ruby-forum.com/t/string-mangling/50243/5 "2005-12-14T14:39:01Z")
On Dec 14, 2005, at 6:32 AM, Simon S. wrote: > irb(main):001:0\> s = ‘aaaaabbccccceeebbbbbbbbbbeaaabaacccceee’ > =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceee” > irb(main):002:0\> s.scan(/(a+)|(b+)|(c+)|([^abc]+)/) > =\> [[“aaaaa”, nil, nil, nil], [nil, “bb”, nil, nil], [nil, nil, > “ccccc”, nil], [nil, nil, nil, “eee”], [nil, “bbbbbbbbbb”, nil, nil], > [nil, nil, nil, “e”], [“aaa”, nil, nil, nil], [nil, “b”, nil, nil], > [“aa”, nil, nil, nil], [nil, nil, “cccc”, nil], [nil, nil, nil, > “eee”]] > irb(main):003:0\> My similar thought: > > str = ‘aaaaabbccccceeebbbbbbbbbbeaaabaacccceee’ > > =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceee” > > > str.scan(/((\w)\2\*)/).map { |chunk| chunk.first } > > =\> [“aaaaa”, “bb”, “ccccc”, “eee”, “bbbbbbbbbb”, “e”, “aaa”, “b”, > > “aa”, “cccc”, “eee”] James Edward G. II ---
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 14, 2005, 2:23pm UTC](https://www.ruby-forum.com/t/string-mangling/50243/6 "2005-12-14T14:23:59Z")
Robert K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > /aaaa/ … > > > > /bbb/ … > > > > /cccc/ … > > > > else > > > > end > > […] > > Or, if you want to avoid a second match: of course I want 🙂 > A > B > C > B > A > B > A > C > =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee” …but this doesn’t allow a processing step in the “else” case? Martin ---
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 14, 2005, 8:39pm UTC](https://www.ruby-forum.com/t/string-mangling/50243/7 "2005-12-14T20:39:37Z")
Martin P. wrote: > Imagine an input string > aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee… > > I have regexp for the parts a,b,c > and e can be considered as else. > > So how can I efficiently search/step through the string from left to > right, while calling for each section the fitting handler, kind of > > case section > /aaaa/ … > > /bbb/ … > > /cccc/ … > > else > > end Aside from the oft-mentioned String#scan, you might look into using StringScanner (require ‘strscan’) from the stdlib. It is very good for more complex cases of scanning. Documentation is available, for example, at [RDoc Documentation](http://www.ruby-doc.org/stdlib). > Thanks for ideas! > Martin E ---
**Author:** ![dhstudio](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b487fb/32.png) [@dhstudio](https://www.ruby-forum.com/u/dhstudio)\ **Post date:** [December 15, 2005, 11:08am UTC](https://www.ruby-forum.com/t/string-mangling/50243/8 "2005-12-15T11:08:10Z")
Martin P. wrote: > > > case section > > > Or, if you want to avoid a second match: > > > > > > > ``` > > > > puts "C" > > > > > > > > ``` > > > > =\> “aaaaabbccccceeebbbbbbbbbbeaaabaacccceeee” > > …but this doesn’t allow a processing step in the “else” case? You can have an else clause - but it will never be called. I guess you will process entries between matches. In that case scan won’t help - at least not as used in my example. A simple option would be to use #split with a group around the whole regexp and then operate on the array of strings you get. Whether that’s feasible (volume?) in you case I cannot decide. s.split(/((?:a+)|(?:b+)|(?:c+))/.each do |m| case section /aaaa/ … /bbb/ … /cccc/ … else end end Kind regards ``` robert ```