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Regular expressions in Ruby and Introduction to Vim
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Regular expressions in Ruby and Introduction to Vim

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What is regular expression and how it can be used in Ruby programming langauge. Also some introduction about VIM editor given.

What is regular expression and how it can be used in Ruby programming langauge. Also some introduction about VIM editor given.

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  • 1. Ruby Regular Expression - Basics
  • 2. Regular Expression Historically, regular expressions are one of computer science's shining examples of how using good theory leads to good programs. Today, regular expressions have also become a shining example of how ignoring good theory leads to bad programs.
  • 3. What is regular expression ● Is a notation for describing a set of character strings ● sequence of characters within /, / ● single character within /, / is the simple regular expression Ex: /hello world/
  • 4. What can be done with regular expression ? ● Test a string to see whether it matches a pattern ● Extract from a string the sections that match all or part of a pattern ● Change the string, replacing parts that match a pattern
  • 5. Metacharcters ● Some characters have special meaning in regular expression – ., |, (, ), [, ], {, }, +, , ^, $, * and ? – ● They don't match themselves ● To match, escape it with '' Ex: '*' =~ /*/
  • 6. Ruby Regular Expressions ● Uses 'Oniguruma' open source C library by K. Kosako ● It also an object, Regexp ● #{...} expression substitutions in the pattern
  • 7. How to create pattern in ruby ? ● // Ex: /hello/ ● Regexp.new Ex: Regexp.new('hello') ● %r{...} Ex: %r{mm/dd}
  • 8. Matching against String “When a particular string is in the set described by a regular expression, we often say that the regular expression matches the string” ● =~ – Returns matched index / nil ● !~ – Returns true / false ● match() – Method of String & Regexp – Returns MatchData object / nil
  • 9. Regular expression options ● i – case insensitive ● m – multiline mode ● x – Extended mode
  • 10. Metacharacters ● Period ( . ) – To match any character – Should be escaped to match literal '.'
  • 11. Metacharacters ● Anchors – To restrict the pattern to match beginning or end of the line – ^ - beginning of the line – $ - end of the line – A – beginning of the string – Z – end of the string
  • 12. Metacharacters ● Character Class – Set of characters between [ and ] – Can have ranges – Can negate character sets ● Sequences d, D, w, W, s, S Ex: ● /[dr]ejected/ ● Match digits [0-9] ● Alphanumeric [A-Za-z0-9] ● Except digits [^0-9] ● Str.gsub(/['”]/,'')
  • 13. Metacharacters ● Repetition – r* Matches zero or more occurrences of r – r+ Matches one or more occurrences of r – r? Matches zero or one occurrence of r – r{m,n} Matches at least m and at most n occurrences of r – r{m,} Matches at least m occurrences of r – r{,n} Matches at most n occurrences of r – r{m } Matches exactly m occurrences of r
  • 14. Metacharacters ● Alternation – | Ex: /red|blue/ ● Grouping – Everything within the group is treated as a single regular expression – Backreferenced by numbers
  • 15. Metacharacters ● Repetition – r* Matches zero or more occurrences of r – r+ Matches one or more occurrences of r – r? Matches zero or one occurrence of r – r{m,n} Matches at least m and at most n occurrences of r – r{m,} Matches at least m occurrences of r – r{,n} Matches at most n occurrences of r – r{m } Matches exactly m occurrences of r
  • 16. Vim Editor - Basics
  • 17. Vim - Intro ● Vim is a text editor written by Bram Moolenaar based on 'vi' ● The original code for 'vi' was written by Bill Joy in 1976 ● Originally created for Unix systems
  • 18. Vim – Modes ● Normal Mode – characters you type are commands – Default mode ● Insert Mode – the characters are inserted as text – I, i, A, a, O, o switch to insert mode – Escp key is to come back to normal mode
  • 19. Vim – Manipulation ● Delete – d – dw, dd, D, x, X ● Copy – y – yw, yy, Y ● Join – J ● Paste – P, p ● Replace – r, R ● Undo & Redo – u, Ctrl+r
  • 20. Vim – Navigation ● h, j, k , l ● w, b, e ● 0, ^, $ – P, p ● G, gg ● % (matches {}()[ ]) ● Ctrl-b, Ctrl-f ● N G ( got to nth line)
  • 21. Vim – Search & Replace ● /pattern ● ?pattern – N, n ● :range s/oldpattern/new/options ● F, f, t, T
  • 22. Vim – Misc ● Surrounding ● Swapcase ● Vim file +pageno ● Set nu, spell ● gf ● autocomplete
  • 23. Vim – Exit ● :q ● :q! ● :wq
  • 24. Thanks