From: RichardOnRails <RichardDummyMailbox58407@...>
Date: 2011-02-24T04:35:26+09:00
Subject: Re: Math module not found by Ruby, though it seems to be loaded

On Feb 23, 4:27 am, Josh Cheek <josh.ch...@gmail.com> wrote:
> [Note:  parts of this message were removed to make it a legal post.]
>
> On Tue, Feb 22, 2011 at 11:55 PM, RichardOnRails <
>
>
>
> RichardDummyMailbox58...@uscomputergurus.com> wrote:
> > When I decided I should come up to speed on Modules,  I found a simple
> > writeup on:
> >http://www.tutorialspoint.com/ruby/ruby_modules.htm.
>
> > The example worked fine as far hooking up the Module routines to the
> > main code went, but it didn't work because the author didn't finish
> > defining some of the methods, which I discovered by running the code.
> > I fleshed out the trig functions by using the math module, but that
> > bombed.
>
> > I posted my code and the error messages athttp://www.pastie.org/1596692.
>
> > I'm running Ruby 1.8.6 over WinXP-Pro/SP3.  I'm stuck on the complaint
> > that the math module cannot be found
>
> > However, the following seems to show that I've got the math module
> > installed:
> > K:\>gem list -l math
>
> > *** LOCAL GEMS ***
>
> > math (0.0.1)
> > mathml (0.8.1)
>
> > So, I can't see what's wrong.  Any ideas?
>
> > Thanks in Advance,
> > Richard
>
> Math is a class defined in core (http://ruby-doc.org/core-1.8.6/classes/Math.html), so it is already there,
> you already have access to it (its not in the stdlib or anything). So you
> can just get rid of the line `require "math"`
>
> However, if you're wanting to use the gem you have installed, you can do
> that by first requiring rubygems, which will be found because it is in the
> standard library. Rubygems will modify the path in such a way to allow your
> ruby to find the math gem when you require it later (assuming gem author
> follows conventions). You don't have to do this in newer versions of Ruby.
>
> Also, it doesn't look like you're doing anything in your code that Math
> can't already handle, so not sure what you are intending to use the gem for.

> so not sure what you are intending to use the gem for.

I mis-read this line when I previously replied.  I thought I had to
install the gem because I didn't know that Math was included in the
Kernel.  I guess I'll leave it installed and use your "rubygems"
invocation if I ever think I have to use it.

But I benefited from your comment about 'rubygems' in that I saw it
used often but never had a clue as to why it was used.  So, thanks for
the "clue".

Best,
Richard