thr3ads.net - Rails - Math parser? [May 2008]

If this information is useful, please help other people find it:
Share via:

Emil Kampp

2008-May-18 18:21 UTC

Math parser?

HI guys.

I need to calculate a string as a math piece. E.i. "100*500/2.5" Is
there a build in parser in the Math class to do this?
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Tor Erik Linnerud

2008-May-18 23:20 UTC

head link

Re: Math parser?

> Is there a build in parser in the Math class to do this?
I don''t think so, but we might roll our own.

module Math
  def self.eval(expression)
    allowed_characters = Regexp.escape(''+-*/.'')
    safe_expression = 
expression.match(/[\d#{allowed_characters}]*/).to_s
    Kernel.eval(safe_expression)
  end
end

I believe the above is safe, but don''t shoot me if it''s not.

Tor Erik

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED ...
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Emil Kampp

2008-May-19 05:17 UTC

head link

Re: Math parser?

Super. Ill try that. I would need to add this to the math class in the 
ruby root library?

Tor Erik Linnerud wrote:>> Is there a build in parser in the Math class to do this?
> 
> I don''t think so, but we might roll our own.
> 
> module Math
>   def self.eval(expression)
>     allowed_characters = Regexp.escape(''+-*/.'')
>     safe_expression = 
> expression.match(/[\d#{allowed_characters}]*/).to_s
>     Kernel.eval(safe_expression)
>   end
> end
> 
> I believe the above is safe, but don''t shoot me if it''s
not.
> 
> Tor Erik
> 
> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS
> OR IMPLIED, INCLUDING BUT NOT LIMITED ...
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Ryan Bigg (Radar)

2008-May-19 05:27 UTC

head link

Re: Math parser?

You can put this file in the lib directory, and call it something simple
like custom_math.rb, then in your application.rb do include Math and it
should include that.

On Mon, May 19, 2008 at 2:47 PM, Emil Kampp <
rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>
> Super. Ill try that. I would need to add this to the math class in the
> ruby root library?
>
> Tor Erik Linnerud wrote:
> >> Is there a build in parser in the Math class to do this?
> >
> > I don''t think so, but we might roll our own.
> >
> > module Math
> >   def self.eval(expression)
> >     allowed_characters = Regexp.escape(''+-*/.'')
> >     safe_expression > >
expression.match(/[\d#{allowed_characters}]*/).to_s
> >     Kernel.eval(safe_expression)
> >   end
> > end
> >
> > I believe the above is safe, but don''t shoot me if
it''s not.
> >
> > Tor Erik
> >
> > THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS
> > OR IMPLIED, INCLUDING BUT NOT LIMITED ...
>
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>

-- 
Appreciated my help?
Reccommend me on Working With Rails
http://workingwithrails.com/person/11030-ryan-bigg

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

AndyV

2008-May-19 15:44 UTC

head link

Re: Math parser?

If you''re willing to wrap it with some error handling you can let
''eval'' take care of it:

eval("100*500/2.5")
=> 20000.0

(It understands parens, too).>> eval("100*(500/2.5)")=> 20000.0



On May 19, 1:27 am, "Ryan Bigg (Radar)"
<radarliste...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> You can put this file in the lib directory, and call it something simple
> like custom_math.rb, then in your application.rb do include Math and it
> should include that.
>
> On Mon, May 19, 2008 at 2:47 PM, Emil Kampp <
>
>
>
> rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>
> > Super. Ill try that. I would need to add this to the math class in the
> > ruby root library?
>
> > Tor Erik Linnerud wrote:
> > >> Is there a build in parser in the Math class to do this?
>
> > > I don''t think so, but we might roll our own.
>
> > > module Math
> > >   def self.eval(expression)
> > >     allowed_characters = Regexp.escape(''+-*/.'')
> > >     safe_expression > > >
expression.match(/[\d#{allowed_characters}]*/).to_s
> > >     Kernel.eval(safe_expression)
> > >   end
> > > end
>
> > > I believe the above is safe, but don''t shoot me if
it''s not.
>
> > > Tor Erik
>
> > > THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
ANY KIND, EXPRESS
> > > OR IMPLIED, INCLUDING BUT NOT LIMITED ...
>
> > --
> > Posted viahttp://www.ruby-forum.com/.
>
> --
> Appreciated my help?
> Reccommend me on Working With
Railshttp://workingwithrails.com/person/11030-ryan-bigg--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Tor Erik Linnerud

2008-May-19 19:38 UTC

head link

Re: Math parser?

AndyV wrote:> If you''re willing to wrap it with some error handling you can let
> ''eval'' take care of it
Just be carefull so you don''t unintentionally allow arbitrary code to
be
executed. (Depending on the use case this may or may not be an issue).

If you change
Regexp.escape(''+-*/.'')

to

Regexp.escape(''+-*/.() '')

then you can use parentheses and spaces in my example too.

Tor Erik
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Lukasz Wrobel

2008-Nov-24 19:17 UTC

head link

Re: Math parser?

> HI guys.
> 
> I need to calculate a string as a math piece. E.i. "100*500/2.5"
Is
> there a build in parser in the Math class to do this?
Hi, I have just written a few blog posts about building a math parser. 
There is an introduction, some basic knowledge about grammars, sample 
implementation written in Ruby and a test suite. You can find these 
posts here:

* http://lukaszwrobel.pl/blog/math-parser-part-1-introduction
* http://lukaszwrobel.pl/blog/math-parser-part-2-grammar
* http://lukaszwrobel.pl/blog/math-parser-part-3-implementation
* http://lukaszwrobel.pl/blog/math-parser-part-4-tests

If you find the code useful, feel free to use it in your own program.
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Rails - May 2008 - Math parser?

Math parser?

Re: Math parser?

Re: Math parser?

Re: Math parser?

Re: Math parser?

Re: Math parser?

Re: Math parser?