# One More Bias (or perhaps I'm too novice ) **URL:** \ **Category:** Ruby\ **Created:** [June 1, 2007, 3:39pm UTC](https://www.ruby-forum.com/t/one-more-bias-or-perhaps-im-too-novice/105701 "2007-06-01T15:39:23Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![vineetraja](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/c57346/32.png) [@vineetraja](https://www.ruby-forum.com/u/vineetraja)\ **Post date:** [June 1, 2007, 3:39pm UTC](https://www.ruby-forum.com/t/one-more-bias-or-perhaps-im-too-novice/105701/1 "2007-06-01T15:39:23Z")
Hi All Another Query To bother you all: 1 class Person 2 def \*(o) 3 puts “One person meets another” 4 end 5 6 def meets (o) 7 puts “One person meets another” 8 end 9 end 10 a= Person.new 11 b=Person.new 12 13 a \* b 14 a.meets b ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ now with above Class the output is: > ruby yet.rb > One person meets another > One person meets another CASE 1 If I replace Line 13 with this: a % b #(or any other operator i.e. $ ^ & et al.) I get the following error : yet.rb:16: undefined method `%’ for #Person:0x282dbf4 (NoMethodError) CASE 2 But when i replaced Line 14 with this: a meets b the error was this > ruby yet.rb > One person meets another > yet.rb:17: warning: parenthesize argument(s) for future version > yet.rb:17: undefined method `meets’ for main:Object (NoMethodError) +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ THE QUERY If a method is encountered then what is order for locating the method in class hierarchy? I mean base to child or reverse? And regardless of that order why ruby tries to locate the “%” method from Person (case 1) while the “meets” method is searched for in Object (case 2) Thanks in Advance Raja Ruby is beautiful! ---
**Author:** ![vineetraja](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/c57346/32.png) [@vineetraja](https://www.ruby-forum.com/u/vineetraja)\ **Post date:** [June 1, 2007, 3:51pm UTC](https://www.ruby-forum.com/t/one-more-bias-or-perhaps-im-too-novice/105701/2 "2007-06-01T15:51:10Z")
On Fri, Jun 01, 2007 at 10:39:23PM +0900, Vin R. wrote: > 10 a= Person.new > > CASE 1 > If I replace Line 13 with this: > a % b #(or any other operator i.e. $ ^ & et al.) > > I get the following error : > yet.rb:16: undefined method `%’ for #Person:0x282dbf4 (NoMethodError) Correct. a % b is syntactic sugar for a.%(b) or a.send(:%, b) That is, invoke a method called ‘%’ on object ‘a’, passing ‘b’ as the argument. > CASE 2 > But when i replaced Line 14 with this: > a meets b > the error was this > > > ruby yet.rb > > One person meets another > > yet.rb:17: warning: parenthesize argument(s) for future version > > yet.rb:17: undefined method `meets’ for main:Object (NoMethodError) If you don’t follow ‘a’ by a dot, then it’s treated as a method name on the local object: that is, self.a(…) So what you have written is a( meets( b ) ) which has an implicit receiver, self.a( meets( b ) ) The receiver, self, is a top-level object called “main”. But you have not defined methods ‘a’ or ‘meets’ at the top level. def a(x) “a:#{x}” end def meets(x) “meets:#{x}” end b = “fred” puts(a meets b) # “a:meets:fred” but with warnings about missing parens puts a(meets(b)) # no warnings Brian. ---
**Author:** ![vineetraja](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/v/c57346/32.png) [@vineetraja](https://www.ruby-forum.com/u/vineetraja)\ **Post date:** [June 1, 2007, 4:45pm UTC](https://www.ruby-forum.com/t/one-more-bias-or-perhaps-im-too-novice/105701/3 "2007-06-01T16:45:22Z")
On 2007-06-01 22:39:23 +0900 (Fri, Jun), Vin R. wrote: > 8 end > > > ruby yet.rb > > CASE 2 > > THE QUERY > > If a method is encountered then what is order for locating the method > in class hierarchy? > I mean base to child or reverse? Always in ‘current’ object, then in its parent and so on. > And regardless of that order why ruby tries to locate the “%” method > from Person (case 1) > > while the “meets” method is searched for in Object (case 2) That’s how hackers learn new languages! I like your style. 🙂 You found the dark side of ruby parser. In your case, the parser has decided that expression ‘a meets b’ is a call to method ‘Object#a’ of ‘self’ (some ‘main’ object). That’s the cause of the warning ‘parenthesize argument(s) for future version’. First step was to get the values of the parameter, which was ‘meets b’, which got understood as a call to Object#meets with parameter ‘b’. The ‘b’ has been taken as a local variable, because of assignment in line 11. Having the value of ‘b’ the call to Object#meets has been executed, which generated the exception. In the expression ‘a % b’ the ‘%’ has been at once recognized as an operator, so the corresponding method has been called on the left side of that operator, thus the error - undefined method on Person. In other words, the parser had decided that ‘a % b’ is: ‘operator % with arguments “a” and “b”’, which is equal to: ‘a.%(b)’ and in ‘a meets b’ meets is not an operator, so it’s a function argument, so ‘a’ is a method call, and there is no ‘meets’ variable (since there was no assignment seen), so ‘meets’ is also a method call, and it needs parentheses, so the result was: ‘a( meets(b) )’, which is: ‘self.a( self.meets(b))’, and self.class is Object.