CODEWITHSUNDEEP
rubyregexrubular
Vincent Cheloudiakoff
Vincent Cheloudiakoff

Reputation: 65

Select a string in regex with ruby

I have to clean a string passed in parameter, and remove all lowercase letters, and all special character except :

so i have this string passed in parameter:

aA azee + B => C=

and i need to clean this string to have this result:

A + B => C

I do

string.gsub(/[^[:upper:][+|^ ]]/, "")

output: "A + B C"

I don't know how to select the => (and for <=>) string's with regex in ruby)

I know that if i add string.gsub(/[^[:upper:][+|^ =>]]/, "") into my regex, the last = in my string passed in parameter will be selected too

Upvotes: 1

Views: 677

Answers (3)

Cary Swoveland
Cary Swoveland

Reputation: 110755

r = /[a-z\s[:punct:]&&[^+ |^]]/

"The cat, 'Boots', had 9+5=4 ^lIVEs^ leF|t.".gsub(r,'')
  #=> "T  B  9+54 ^IVE^ F|"

The regular expression reads, "Match lowercase letters, whitespace and punctuation that are not the characters '+', ' ', '|' and '^'. && within a character class is the set intersection operator. Here it intersects the set of characters that match a-z\s[:punct:] with those that match [^+ |^]. (Note that this includes whitespaces other than spaces.) For more information search for "character classes also support the && operator" in Regexp.

I have not included '=>' and '<=>' as those, unlike '+', ' ', '|' and '^', are multi-character strings and therefore require a different approach than simply removing certain characters.

Upvotes: 0

Sweeper
Sweeper

Reputation: 274480

You can try an alternative approach: matching everything you want to keep then joining the result.

You can use this regex to match everything you want to keep:

[A-Z\d+| ^]|<?=>

As you can see this is just a using | and [] to create a list of strings that you want to keep: uppercase, numbers, +, |, space, ^, => and <=>.

Example:

"aA azee + B => C=".scan(/[A-Z\d+| ^]|<?=>/).join()

Output:

"A  + B => C"

Note that there are 2 consecutive spaces between "A" and "+". If you don't want that you can call String#squeeze.

Upvotes: 5

ctwheels
ctwheels

Reputation: 22837

See regex in use here

(<?=>)|[^[:upper:]+|^ ]
  • (<?=>) Captures <=> or => into capture group 1
  • [^[:upper:]+|^ ] Matches any character that is not an uppercase letter (same as [A-Z]) or +, |, ^ or a space

See code in use here

p "aA azee + B => C=".gsub(/(<?=>)|[^[:upper:]+|^ ]/, '\1')

Result: A + B => C

Upvotes: 1

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