Yeah, it's whether it reads from a variable or calls a method. e.g.:
def blah x # equivalent to x() if x is in scope, otherwise "no method defined" end def blob x = 1 x # reads local variable end and thanks to the source of these emails def bozo x = x # returns nil, never calls x() end Looking into it a bit more, I was wrong; it's done at parse time, but per-statement. So x = x is fine, because it's defined and used in the same statement. Any read of x in a statement before it's assigned will fail (or be a method call). So the following does not work: def bling return x # undefined local variable or method `x' (if x isn't defined elsewhere) x = 1 end On Thu, Jan 14, 2016 at 4:59 PM, Ryan Bigg <[email protected]> wrote: > I think what you're referring to is if it checks for a local variable or > method, which only happens when you call it. > > > > On 14 Jan 2016, at 15:39, Clifford Heath <[email protected]> > wrote: > > > > Ugh, yes, sorry, brain fart, I’m thinking of something else. > > What’s the thing where the parser has to check local usage to decide > syntax? > > There’s definitely a reason Ruby needs to know about local variables, > even > > if they’re only mentioned in conditional code that’s not hit. > > > > Clifford Heath. > > > >> On 14 Jan 2016, at 12:00 PM, Ryan Bigg <[email protected]> wrote: > >> > >> It won't ever do self.send(:x=, 3). x = 3 is always a local variable > assignment. > >> > >>>> On 14 Jan 2016, at 11:52, Clifford Heath <[email protected]> > wrote: > >>>> > >>>> On 14 Jan 2016, at 9:19 AM, Simon Russell <[email protected]> > wrote: > >>>> I'd say this "feature" probably has no useful purpose; I can't > imagine a language designer deliberately putting it in. It's more likely > to cause bugs than joy. > >>>> I'm not certain, but I'm fairly your "unintended parser > functionality" is heading in the right direction. > >>> > >>> No. I think it’s a necessary feature of the Ruby syntax. When Ruby > sees “x = 3”, it needs to decide whether you want an assignment to a local > variable, or “self.send(:x=, 3)”. > >>> > >>> So it looks around the local scope for clues about what you meant, and > when it decides that a word is the name of a local variable, it treats it > that way throughout the function. > >>> > >>> Clifford Heath. > >>> > >>>> From memory working on a Ruby compiler, Ruby allocates local > variables before execution, but doesn't mark where they become "real". So > they're essentially real from the start, and get assigned a default value > of nil. It makes the whole thing easier to build; it's kind of a shortcut. > >>>> > >>>> So, moral of this story is... Don't assign things twice? Makes for > a better design anyway! :) > >>>> > >>>> On Thu, Jan 14, 2016 at 5:35 AM, Gareth Townsend < > [email protected]> wrote: > >>>> Rubocop has a linter for shadowing variables; > >>>> > >>>> > http://www.rubydoc.info/github/bbatsov/rubocop/Rubocop/Cop/Lint/ShadowingOuterLocalVariable > >>>> > >>>> Gareth Townsend > >>>> http://www.garethtownsend.info > >>>> > >>>>> On 13 Jan 2016, at 22:00, David Parry <[email protected]> > wrote: > >>>>> > >>>>> Shadowing variables, which is effectively what you’ve done with > “misspelt_argument”, is pretty-much always a bad idea in most languages. > >>>>> > >>>>> In functional languages, it’s mostly impossible to do without the > compiler complaining, and for very good reasons, one of which you’ve > pointed out. > >>>>> > >>>>> I suspect that tools like RuboCop would probably pick this sort of > abomination up. Anyone know if that’s the case? > >>>>> > >>>>> > >>>>> > >>>>>> On 13 Jan 2016, at 8:41 PM, Tom Hale <[email protected]> wrote: > >>>>>> > >>>>>> It took some debugging to come across this one: > >>>>>> > >>>>>> irb(main):043:0> w > >>>>>> NameError: undefined local variable or method `w' for main:Object > >>>>>> from (irb):43 > >>>>>> from /home/ravi/.rbenv/versions/2.2.3/bin/irb:11:in `<main>' > >>>>>> irb(main):044:0> w = w > >>>>>> => nil > >>>>>> irb(main):045:0> > >>>>>> > >>>>>> Yeah, right, so what? > >>>>>> > >>>>>> It leads to "find the nil" fun-hunts in cases such as: > >>>>>> > >>>>>> irb(main):057:0> mispelt_argument = > Array(mispelt_argument).flatten.uniq.map(&:name) > >>>>>> => [] > >>>>>> > >>>>>> Are there any cases in which this "feature" is actually useful, or > is it an unintended parser functionality? > >>>>>> > >>>>>> Tom > >>>>>> > >>>>>> -- > >>>>>> You received this message because you are subscribed to the Google > Groups "Ruby or Rails Oceania" group. > >>>>>> To unsubscribe from this group and stop receiving emails from it, > send an email to [email protected]. > >>>>>> To post to this group, send email to [email protected] > . > >>>>>> Visit this group at https://groups.google.com/group/rails-oceania. > >>>>>> For more options, visit https://groups.google.com/d/optout. > >>>>> > >>>>> -- > >>>>> You received this message because you are subscribed to the Google > Groups "Ruby or Rails Oceania" group. > >>>>> To unsubscribe from this group and stop receiving emails from it, > send an email to [email protected]. > >>>>> To post to this group, send email to [email protected]. > >>>>> Visit this group at https://groups.google.com/group/rails-oceania. > >>>>> For more options, visit https://groups.google.com/d/optout. > >>>> > >>>> -- > >>>> You received this message because you are subscribed to the Google > Groups "Ruby or Rails Oceania" group. > >>>> To unsubscribe from this group and stop receiving emails from it, > send an email to [email protected]. > >>>> To post to this group, send email to [email protected]. > >>>> Visit this group at https://groups.google.com/group/rails-oceania. > >>>> For more options, visit https://groups.google.com/d/optout. > >>>> > >>>> > >>>> -- > >>>> You received this message because you are subscribed to the Google > Groups "Ruby or Rails Oceania" group. > >>>> To unsubscribe from this group and stop receiving emails from it, > send an email to [email protected]. > >>>> To post to this group, send email to [email protected]. > >>>> Visit this group at https://groups.google.com/group/rails-oceania. > >>>> For more options, visit https://groups.google.com/d/optout. > >>> > >>> -- > >>> You received this message because you are subscribed to the Google > Groups "Ruby or Rails Oceania" group. > >>> To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > >>> To post to this group, send email to [email protected]. > >>> Visit this group at https://groups.google.com/group/rails-oceania. > >>> For more options, visit https://groups.google.com/d/optout. > >> > >> -- > >> You received this message because you are subscribed to the Google > Groups "Ruby or Rails Oceania" group. > >> To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > >> To post to this group, send email to [email protected]. > >> Visit this group at https://groups.google.com/group/rails-oceania. > >> For more options, visit https://groups.google.com/d/optout. > > > > -- > > You received this message because you are subscribed to the Google > Groups "Ruby or Rails Oceania" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > > To post to this group, send email to [email protected]. > > Visit this group at https://groups.google.com/group/rails-oceania. > > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "Ruby or Rails Oceania" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/rails-oceania. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Ruby or Rails Oceania" group. 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