Where Is Ruby'S String Literal Juxtaposition Feature Officially Documented

Where is Ruby's string literal juxtaposition feature officially documented?

UPDATE

This is now officially documented in the RDoc that ships with Ruby.

Changes will propagate to RubyDoc the next time they build the documentation.

The added documentation:

Adjacent string literals are automatically concatenated by the interpreter:

"con" "cat" "en" "at" "ion" #=> "concatenation"
"This string contains "\
"no newlines." #=> "This string contains no newlines."

Any combination of adjacent single-quote, double-quote, percent strings will
be concatenated as long as a percent-string is not last.

%q{a} 'b' "c" #=> "abc"
"a" 'b' %q{c} #=> NameError: uninitialized constant q

ORIGINAL

Right now, this isn't anywhere in the official ruby documentation, but I think it should be. As pointed out in a comment, the logical place for the docs to go would be: http://www.ruby-doc.org/core-2.0/doc/syntax/literals_rdoc.html#label-Strings

I've opened a pull request on ruby/ruby with the documentation added.

If this pull request is merged, it will automatically update http://www.ruby-doc.org. I'll update this post if/when that happens. ^_^

The only other mentions of this I've found online are:

  • The Ruby Programming Language, page 47 (mentioned in another answer)
  • Ruby Forum Post circa 2008
  • Programming Ruby

Why does ruby automatically combine Strings?

Yes. From Literals: String

Adjacent string literals are automatically concatenated by the interpreter:

"con" "cat" "en" "at" "ion" 
#=> "concatenation"
"This string contains " "no newlines."
#=> "This string contains no newlines."

Surprising string concatenation

This only works for string literals, and a part of the literal syntax.

If you have 2 string literals with just whitespace between them, they get turned into a single string. It's a convention borrowed from later versions of C.

String object to array ruby

"{1,22,33,444}".scan(/\d+/) #=> ["1", "22", "33", "444"]

should do it.

Why do two strings separated by space concatenate in Ruby?

Implementation details can be found in parse.y file in Ruby source code. Specifically, here.

A Ruby string is either a tCHAR (e.g. ?q), a string1 (e.g. "q", 'q', or %q{q}), or a recursive definition of the concatenation of string1 and string itself, which results in string expressions like "foo" "bar", 'foo' "bar" or ?f "oo" 'bar' being concatenated.

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