# Why does the eql? method exist? **URL:** \ **Category:** Ruby\ **Created:** [October 19, 2006, 8:01am UTC](https://www.ruby-forum.com/t/why-does-the-eql-method-exist/72832 "2006-10-19T08:01:53Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![maz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@maz](https://www.ruby-forum.com/u/maz)\ **Post date:** [October 19, 2006, 8:01am UTC](https://www.ruby-forum.com/t/why-does-the-eql-method-exist/72832/1 "2006-10-19T08:01:53Z")
Not too long ago, there was a thread about a bug in Ruby where vectors (which turned out to be derived from matrices) failed to work as hash keys. The problem turned out to be a typo in the definition of the Matrix class. The method “eql?” is used by hashes for key comparison but, in the Matrix class, this method was named “eqn?” by mistake. This got me thinking about the role of the “eql?” method. Why does it exist? What is the Ruby rationale behind having two different equality methods, namely “==” and “eql?” Thank you… ---
**Author:** ![maz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@maz](https://www.ruby-forum.com/u/maz)\ **Post date:** [October 19, 2006, 11:57am UTC](https://www.ruby-forum.com/t/why-does-the-eql-method-exist/72832/2 "2006-10-19T11:57:13Z")
Just Another Victim of the Ambient M. wrote: > ``` > This got me thinking about the role of the "eql?" method. Why does it > > ``` > > exist? What is the Ruby rationale behind having two different equality > methods, namely “==” and “eql?” > Thank you… ri Object#eql? ``` ... The +eql?+ method returns +true+ if _obj_ and _anObject_ have the same value. Used by +Hash+ to test members for equality. For objects of class +Object+, +eql?+ is synonymous with +==+. Subclasses normally continue this tradition, but there are exceptions. +Numeric+ types, for example, perform type conversion across +==+, but not across +eql?+, so: 1 == 1.0 #=> true 1.eql? 1.0 #=> false ``` Greetings, Esad ---
**Author:** ![maz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@maz](https://www.ruby-forum.com/u/maz)\ **Post date:** [October 19, 2006, 4:37pm UTC](https://www.ruby-forum.com/t/why-does-the-eql-method-exist/72832/3 "2006-10-19T16:37:54Z")
On 10/19/06, Just Another Victim of the Ambient M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ``` > Not too long ago, there was a thread about a bug in Ruby where vectors > > ``` > > (which turned out to be derived from matrices) failed to work as hash keys. > The problem turned out to be a typo in the definition of the Matrix class. > The method “eql?” is used by hashes for key comparison but, in the Matrix > class, this method was named “eqn?” by mistake. > This got me thinking about the role of the “eql?” method. Why does it > exist? What is the Ruby rationale behind having two different equality > methods, namely “==” and “eql?” Most languages provide many equality operators, as depending on context different kind of “equality” is needed. Obviously we want 1.0 == 1 to be true, right ? And as obviously, we want a\_hash[1.0] and a\_hash[1] to be different. So we have == and eql?, and even equal? for “is-it-the-same-object”.