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Just trying to debug a regular expression in ruby. When I print the contents of a regular expression, it shows ?-mix at the beginning of the regular expression even though those characters were not part of the expression. Please see the following IRB output to see this illustrated
irb(main):028:0* EXPR = /^a$/ => /^a$/ irb(main):029:0> EXPR => /^a$/ irb(main):030:0> puts EXPR (?-mix:^a$) => nil As you can see, when you use puts to print out the contents of a regular expression, there is ?-mix at the beginning. Should I be concerned by this? Where is it coming from?
601
=~ is Ruby's pattern-matching operator. It matches a regular expression on the left to a string on the right. If a match is found, the index of first match in string is returned. If the string cannot be found, nil will be returned.
A regular expression is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings. Ruby regular expressions i.e. Ruby regex for short, helps us to find particular patterns inside a string. Two uses of ruby regex are Validation and Parsing.
Ruby | Regexp match() function Regexp#match() : force_encoding?() is a Regexp class method which matches the regular expression with the string and specifies the position in the string to begin the search.
mix is not the English word mix, it's options of Regexp.
See Regexp#to_s:
Returns a string containing the regular expression and its options (using the (
?opts:source) notation.
In your example, m is for multiline mode, i is for case insensitive, and x is for extended mode. Options before the dash are on, those after are off (default). The question's example, ?-mix, has all options off.
You can turn them on like:
puts /^a$/mix # =>(?mix:^a$) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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