[ACCEPTED]-What is the difference between %w{} and %W{} upper and lower case percent W array literals in Ruby?-ruby
%W treats the strings as double quoted whereas 4 %w treats them as single quoted (and therefore 3 won’t interpolate expressions or numerous 2 escape sequences). Try your arrays again 1 with ruby expressions and you'll see a difference.
EXAMPLE:
myvar = 'one'
p %w{#{myvar} two three 1 2 3} # => ["\#{myvar}", "two", "three", "1", "2", "3"]
p %W{#{myvar} two three 1 2 3} # => ["one", "two", "three", "1", "2", "3"]
Let's skip the array confusion and talk 3 about interpolation versus none:
irb(main):001:0> [ 'foo\nbar', "foo\nbar" ]
=> ["foo\\nbar", "foo\nbar"]
irb(main):002:0> [ 'foo\wbar', "foo\wbar" ]
=> ["foo\\wbar", "foowbar"]
The difference 2 in behavior is consistent with how single-quoted 1 versus double-quoted strings behave.
To demonstrate a case with interpolation and sequence escape for both 1 literals, we assume that:
>> a = 'a'
=> "a"
The lower-case %w percent literal:
>> %w[a#{a} b#{'b'} c\ d \s \']
=> ["a\#{a}", "b\#{'b'}", "c d", "\\s", "\\'"]
- treats all supplied words in the brackets as single-quoted Strings
- does not interpolate Strings
- does not escape sequences
- escapes only whitespaces by
\
The upper-case %W percent literal:
>> %W[a#{a} b#{'b'} c\ d \s \']
=> ["aa", "bb", "c d", " ", "'"]
- treats all supplied words in the brackets as double-quoted Strings
- allows String interpolation
- escapes sequences
- escapes also whitespaces by \
Source: What is the difference between %w and %W array literals in Ruby
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