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rubycompatibilityruby-1.9ruby-1.8

Why does this code work in ruby 1.8 and not ruby 1.9?

This piece of code:

def func *; end
[func "hello"]

is parsed without error in Ruby 1.8.7, but returns a syntax error:

syntax error, unexpected ']', expecting '}'

in Ruby >= 1.9. I looked through What is the difference between Ruby 1.8 and Ruby 1.9, but couldn't find a reference to this. Does anyone know what change is causing this?

Solution

  • It's to avoid ambiguity. Consider the following:

    def foo(a, b = 1) # foo takes an optional second argument
end

[foo 1, 2]

    This could be interpreted as [(foo 1), 2] or as [(foo 1, 2)].

    There are two references in the Calling Methods docs (although not directly related to the array literal):

    Note that the parenthesis are optional ... Except when there is difference between using and omitting parentheses

    In many cases parenthesis are not necessary when sending a message ... However, parenthesis are necessary to avoid ambiguity.