# How to call operator as function **URL:** \ **Category:** ruby-talk\ **Created:** [15 November 2008 10:56 UTC](https://rubytalk.org/t/how-to-call-operator-as-function/50187 "2008-11-15T10:56:19Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Vladimir\_Fekete](https://avatars.discourse-cdn.com/v4/letter/v/a4c791/32.png) [@Vladimir\_Fekete](https://rubytalk.org/u/Vladimir_Fekete)\ **Post date:** [15 November 2008 10:56 UTC](https://rubytalk.org/t/how-to-call-operator-as-function/50187/1 "2008-11-15T10:56:19Z")
Hi \*, could you help me please ? I'm trying to write a code where I could have operators' functions as values of hash and executing them in way like this (formal code): > **路路路** > > #============================= > operators = { "+" =\> Fixnum.+, >               "-" =\> Fixnum.-, >               "++" =\> Myclass.++} > > op = "+" > > result = operators[op](left,right) if left.class==Fixnum and right.class==Fixnum > #============================ > > is it possible ? Thanks, > > Cheers, > > V. ---
**Author:** ![Peter\_Szinek3](https://avatars.discourse-cdn.com/v4/letter/p/ea5d25/32.png) [@Peter\_Szinek3](https://rubytalk.org/u/Peter_Szinek3)\ **Post date:** [15 November 2008 11:05 UTC](https://rubytalk.org/t/how-to-call-operator-as-function/50187/2 "2008-11-15T11:05:49Z")
++ is not supported by Ruby 馃檪 I would do 1.send '+'.to\_sym, 2 unless you want to use some esoteric operator mappings, you don't need the hash. Fixnum.+ doesn't make that much sense because of Ruby's duck typing (and why would you want to restrict yourself to work with just certain objects?) p.s.: dobre tu vidiet matfyzaka 馃檪 Cheers, Peter > **路路路** > > On 2008.11.15., at 11:56, Vladimir Fekete wrote: > > > Hi \*, > > > > could you help me please ? I'm trying to write a code where I could have > > operators' functions as values of hash and executing them in way like this > > (formal code): > > > > #============================= > > operators = { "+" =\> Fixnum.+, > >              "-" =\> Fixnum.-, > >              "++" =\> Myclass.++} > > > > op = "+" > > > > result = operators[op](left,right) if left.class==Fixnum and right.class==Fixnum > > #============================ > > \_\_\_ > [http://www.rubyrailways.com](http://www.rubyrailways.com) ---
**Author:** ![Stefan\_Lang1](https://avatars.discourse-cdn.com/v4/letter/s/46a35a/32.png) [@Stefan\_Lang1](https://rubytalk.org/u/Stefan_Lang1)\ **Post date:** [15 November 2008 11:06 UTC](https://rubytalk.org/t/how-to-call-operator-as-function/50187/3 "2008-11-15T11:06:50Z")
Use send, if all operators are binary:   left.send(:+, right)   left.send(:-, right) etc. Stefan > **路路路** > > 2008/11/15 Vladimir Fekete \: > > > Hi \*, > > > > could you help me please ? I'm trying to write a code where I could have > > operators' functions as values of hash and executing them in way like this > > (formal code): > > > > #============================= > > operators = { "+" =\> Fixnum.+, > >              "-" =\> Fixnum.-, > >              "++" =\> Myclass.++} > > > > op = "+" > > > > result = operators[op](left,right) if left.class==Fixnum and right.class==Fixnum > > #============================ > > > > is it possible ? Thanks, ---
**Author:** ![Sebastian\_Hungereck1](https://avatars.discourse-cdn.com/v4/letter/s/3ab097/32.png) [@Sebastian\_Hungereck1](https://rubytalk.org/u/Sebastian_Hungereck1)\ **Post date:** [15 November 2008 11:07 UTC](https://rubytalk.org/t/how-to-call-operator-as-function/50187/4 "2008-11-15T11:07:17Z")
Vladimir Fekete wrote: > operators = { "+" =\> Fixnum.+, >               "-" =\> Fixnum.-, "+" =\> Fixnum.instance\_method(:+), "-" =\> Fixnum.instance\_method(:-), > ``` > "\+\+" => Myclass\.\+\+\} > > ``` There is no ++ operator in ruby and you can't define one. > op = "+" > > result = operators[op](left,right) if left.class==Fixnum and > right.class==Fixnum result = operators[op].bind(left).call(right) if left.is\_a?(Fixnum) and right.is\_a?(Fixnum) Or you skip the whole thing with the hash and just do: op = "+" result = left.send(op, right) HTH, Sebastian > **路路路** > > -- > Jabber: sepp2k@jabber.org > ICQ: 205544826 ---
**Author:** ![Vladimir\_Fekete](https://avatars.discourse-cdn.com/v4/letter/v/a4c791/32.png) [@Vladimir\_Fekete](https://rubytalk.org/u/Vladimir_Fekete)\ **Post date:** [15 November 2008 11:15 UTC](https://rubytalk.org/t/how-to-call-operator-as-function/50187/5 "2008-11-15T11:15:42Z")
> Vladimir Fekete wrote: > \> operators = { "+" =\> Fixnum.+, > \> "-" =\> Fixnum.-, > > "+" =\> Fixnum.instance\_method(:+), > "-" =\> Fixnum.instance\_method(:-), > > \> ? ? ? ? ? ? ? "++" =\> Myclass.++} > > There is no ++ operator in ruby and you can't define one. it's Myclasses ++ operator > \> op = "+" > \> > \> result = operators[op](left,right) ?if left.class==Fixnum and > \> right.class==Fixnum > > result = operators[op].bind(left).call(right) if left.is\_a?(Fixnum) and > right.is\_a?(Fixnum) > > Or you skip the whole thing with the hash and just do: > > op = "+" > result = left.send(op, right) > > HTH, > Sebastian > -- > Jabber: sepp2k@jabber.org > ICQ: 205544826 What I'm trying to do is Domain specific language class, for which I could set up names of variables, functions and operators and then parse and execute a string (f.e. "( a + ( b \* c ) + sin ( d ) )", where variables could be hash { "a" =\> 1, "b" =\> 2, "c" =\> 3, "d" =\> 4} and functions could be hash again so naturaly I asked whether it is possible to make it with operators). I tryied to use som ruby's or irb's native DSL but withouth success. V. > **路路路** > > On Sat, Nov 15, 2008 at 08:07:17PM +0900, Sebastian Hungerecker wrote: ---
**Author:** ![Sebastian\_Hungereck1](https://avatars.discourse-cdn.com/v4/letter/s/3ab097/32.png) [@Sebastian\_Hungereck1](https://rubytalk.org/u/Sebastian_Hungereck1)\ **Post date:** [15 November 2008 11:20 UTC](https://rubytalk.org/t/how-to-call-operator-as-function/50187/6 "2008-11-15T11:20:38Z")
Vladimir Fekete wrote: > it's Myclasses ++ operator You can't define ++ on any class. You just can't. If the parser sees ++ anywhere it interprets it as two calls to +@ or one call to + and one to +@. HTH, Sebastian > **路路路** > > -- > NP: Dire Straits - Your Latest Trick > Jabber: sepp2k@jabber.org > ICQ: 205544826