# Unintentional hype of Ruby irb and ri **URL:** \ **Category:** ruby-talk\ **Created:** [30 March 2006 17:33 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253 "2006-03-30T17:33:43Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Stephen\_Tashiro](https://avatars.discourse-cdn.com/v4/letter/s/e47774/32.png) [@Stephen\_Tashiro](https://rubytalk.org/u/Stephen_Tashiro)\ **Post date:** [30 March 2006 17:33 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/1 "2006-03-30T17:33:43Z")
Perhaps an inflamatory title - but it answers some simple questions. Having looked at the Pixaxe book and visited various websites with Ruby tutorials, I think there is an unintentional hype of certain Ruby features. We may blame this on the distributors of software. For example, the authors tell us how easy it is to use irb. On my Redhat Enterprise Linux machine, ruby puts("Hello World") ran fine. But irb was not a command known to bash. The redhat distribution has the packages: ruby-docs-1.8.1-7.EL4.2 ruby-tcltk-1.8.1-7.EL4.2 ruby-1.8.1-7.EL4.2 ruby-mode-1.8.1-7.EL4.2 ruby-devel-1.8.1-7.EL4.2 ruby-libs-1.8.1-7.EL4.2 irb-1.8.1-7.EL4.2 So you might get ruby but not irb. The authors extol the virtues of ri. I found that ri File (or ri almost anything) gave: No ri documentation found in:      /usr/share/ri/1.8/system      /usr/share/ri/1.8/site      /root/.rdoc These problems can be blamed on incompetent packaging or installation of Ruby, but it seems to me that the authors of Ruby tutorials should warn their readers about such problems and perhaps give some hints about how to resolve them. In Redhat Enterprise Linux 4, I was able to resolve the irb problem simply by installing the irb-1.8.1-7 package. At to the ri problem,I found no tutorials that mention rdoc or configure ri. Reading the output of ri -h I concluded it would suffice to run rdoc --ri which creates a director called "doc" in my home directory. And this makes ri work for the basic ruby objects. (Of course a more efficient way on a mult-user system would be to create this "doc" file in only one location and direct the ri for each user to it. It would be nice to have a simple example of this. ) ---
**Author:** ![Ara.T.Howard6](https://avatars.discourse-cdn.com/v4/letter/a/958977/32.png) [@Ara.T.Howard6](https://rubytalk.org/u/Ara.T.Howard6)\ **Post date:** [30 March 2006 17:59 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/2 "2006-03-30T17:59:19Z")
we use rhe on all our machines and i can tell you this: the rh ruby rpms are broken, broken, broken, broken - do not use them and please complain to redhat (i have several times). all the issues you are seeing are resolved by using almost any installation method besides rhe rpms. it even works on fedora. i manage about 50 machines and we've taken the compile route - however, since all the boxes see a common nfs mount we install only once there. rhe rpms are really really bad in general and should be avoided - for example the image magic packages break (silently) loseless compression of jp2s... the perl rpm has a userland kernel panic causing bug, etc, etc. we use plain vanilla rhe, installing anything 'important' via compilation and have 100% success with this approach. it's also immune to the auto-upgrade of enterprise systems breaking 24x7 systems on a late sunday evening. the reality is that there is exactly one method of installing ruby, or anything else for that matter, that will work on any platform:    ./configure --prefix=dst && make && sudo make install this becomes \_\_really\_\_ important once one starts installing gems that auto-compile and then upgrade ruby using rpms - only to have all gems start giving bus errors... correct compilation avoids this entirely in addition to allowing multiple ruby versions to be installed (which we require). sad. but true. regards. -a > **···** > > On Fri, 31 Mar 2006 stephen.tashiro@us.army.mil wrote: > > > Perhaps an inflamatory title - but it answers some simple questions. > > > > Having looked at the Pixaxe book and visited various websites with Ruby > > tutorials, I think there is an unintentional hype of certain Ruby > > features. We may blame this on the distributors of software. For > > example, the authors tell us how easy it is to use irb. On my Redhat > > Enterprise Linux machine, ruby puts("Hello World") ran fine. But irb > > was not a command known to bash. The redhat distribution has the > > packages: > > ruby-docs-1.8.1-7.EL4.2 > > ruby-tcltk-1.8.1-7.EL4.2 > > ruby-1.8.1-7.EL4.2 > > ruby-mode-1.8.1-7.EL4.2 > > ruby-devel-1.8.1-7.EL4.2 > > ruby-libs-1.8.1-7.EL4.2 > > irb-1.8.1-7.EL4.2 > > So you might get ruby but not irb. > > > > The authors extol the virtues of ri. I found that ri File (or ri > > almost anything) gave: > > No ri documentation found in: > >     /usr/share/ri/1.8/system > >     /usr/share/ri/1.8/site > >     /root/.rdoc > > > > These problems can be blamed on incompetent packaging or installation > > of Ruby, but it seems to me that the authors of Ruby tutorials should > > warn their readers about such problems and perhaps give some hints > > about how to resolve them. > > > > In Redhat Enterprise Linux 4, I was able to resolve the irb problem > > simply by installing the irb-1.8.1-7 package. > > > > At to the ri problem,I found no tutorials that mention rdoc or > > configure ri. Reading the output of > > ri -h > > I concluded it would suffice to run > > rdoc --ri > > which creates a director called "doc" in my home directory. And this > > makes ri work for the basic ruby objects. (Of course a more efficient > > way on a mult-user system would be to create this "doc" file in only > > one location and direct the ri for each user to it. It would be nice > > to have a simple example of this. ) > > -- > share your knowledge. it's a way to achieve immortality. > - h.h. the 14th dali lama ---
**Author:** ![Hans\_Fugal3](https://avatars.discourse-cdn.com/v4/letter/h/34f0e0/32.png) [@Hans\_Fugal3](https://rubytalk.org/u/Hans_Fugal3)\ **Post date:** [30 March 2006 18:28 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/3 "2006-03-30T18:28:43Z")
I can second that. I have never worked with a more frustrating distribution than R\_HEL\_ (emphasis added). > **···** > > ara.t.howard@noaa.gov wrote: > > > we use rhe on all our machines and i can tell you this: the rh ruby rpms are > > broken, broken, broken, broken - do not use them and please complain to redhat > > (i have several times). > > > > all the issues you are seeing are resolved by using almost any installation > > method besides rhe rpms. it even works on fedora. > > > > i manage about 50 machines and we've taken the compile route - however, since > > all the boxes see a common nfs mount we install only once there. > > > > rhe rpms are really really bad in general and should be avoided - for example > > the image magic packages break (silently) loseless compression of jp2s... the > > perl rpm has a userland kernel panic causing bug, etc, etc. > > > > we use plain vanilla rhe, installing anything 'important' via compilation and > > have 100% success with this approach. it's also immune to the auto-upgrade of > > enterprise systems breaking 24x7 systems on a late sunday evening. > > > > the reality is that there is exactly one method of installing ruby, or > > anything else for that matter, that will work on any platform: > > > >   ./configure --prefix=dst && make && sudo make install > > > > this becomes \_\_really\_\_ important once one starts installing gems that > > auto-compile and then upgrade ruby using rpms - only to have all gems start > > giving bus errors... correct compilation avoids this entirely in addition to > > allowing multiple ruby versions to be installed (which we require). > > > > sad. but true. ---
**Author:** ![Randy\_Kramer](https://avatars.discourse-cdn.com/v4/letter/r/dbc845/32.png) [@Randy\_Kramer](https://rubytalk.org/u/Randy_Kramer)\ **Post date:** [30 March 2006 22:08 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/4 "2006-03-30T22:08:32Z")
Hmm, interesting idea--tell me more:    \* Is that partition mounted as one of the standard partitions (/usr...) or something else?    \* Do you have to do anything on each of those 50 machines, or just mount the NFS partition--hmm, I guess you'd at least have to add something to the PATH of each user (at least, if a non-standard partition)? I might try this, or even on a local non-standard partition (I guess I just have to set the prefix appropriately). This might solve some problems for me--I'm trying to get TkHTML working for me, and by now I'm concerned that I've tried so many things I've created more problems for myself--I could start completely over on a new partition. Then I guess I'd have to do the ./configure --prefix=dst && make && sudo make install process for: Ruby tcltk (or ActiveTcl) TkHTML (although in reading the instructions for this I realize there are some special things to deal with, like the "parallel" bld directory) More info: Part of my problem is that I've compiled Ruby, then installed ActiveTcl, and I don't know how to uninstall something that I installed by compiling. ActiveTcl seemed to have an uninstall.tcl script, but that failed for me. I guess I'll just go around and delete all files and directories that look like they have anything to do with Ruby, tcltk, ActiveTcl, or TkHTML, and then start over. This is on a Mandriva2006 system. I don't know whether the rpms on Mandriva are to blame in any way--I suspect most of the problem(s) are just my ignorance/inexperience in setting something like this up. Randy Kramer > **···** > > On Thursday 30 March 2006 12:59 pm, ara.t.howard@noaa.gov wrote: > > > i manage about 50 machines and we've taken the compile route - however, > > since all the boxes see a common nfs mount we install only once there. ---
**Author:** ![Stephen\_Tashiro](https://avatars.discourse-cdn.com/v4/letter/s/e47774/32.png) [@Stephen\_Tashiro](https://rubytalk.org/u/Stephen_Tashiro)\ **Post date:** [30 March 2006 23:33 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/5 "2006-03-30T23:33:42Z")
I tried the suggestion of installing from source and I like the result better. (My suggestion to run rdoc --ri is only useful if you run it in some directory whose tree contains the source code (\*.c) files for Ruby. ) After an install from source with ../configure make su make install The ri and irb commands work fine. But when I try to use FxRuby, the extension for the Fox Gui Toolkit, there are problems. The extension wants the library libruby.so, which is missing. I tried make distclean ../configure --enable-shared --enable-install-doc --enable-pthread (As if I really knew what I was doing !) make make install-all Then I had a libruby.so and ruby, irb and ri still worked. However the elementary test > require 'fox14' fails since it cannot find the files fox14/core.rb and fox14/core.so. An strace of this process shows it is looking in the correct path for the files. (I resorted to running irb in the fox14 directory.) The problem is that the files were not produced when I compiled fox-1.4.32. I'll be delighted if someone can tell me the answer to that problem. However to return to generalities: I think people trying to use Ruby face more of a challenge than Perl and Python users since they are less likely to find Ruby installed and ready-to-go. In the current epoch, writers of tutorials would do better to give detailed coverage of installation problems. Otherwise the pages about how easy and nice Ruby is will seem a fraud. For example, if you read the typical exposition of the require 'xyz' "command, it doesn't explain how the name 'xyz' is connected to any file on the machine. By experiment it seems to search for a directory named 'xyz'. What paths does it take? What files does it need in that directory? If everything is perfectly installed you don't have to worry about this, but in practice you do. ---
**Author:** ![Ara.T.Howard6](https://avatars.discourse-cdn.com/v4/letter/a/958977/32.png) [@Ara.T.Howard6](https://rubytalk.org/u/Ara.T.Howard6)\ **Post date:** [30 March 2006 22:21 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/6 "2006-03-30T22:21:49Z")
> > i manage about 50 machines and we've taken the compile route - however, > > since all the boxes see a common nfs mount we install only once there. > > Hmm, interesting idea--tell me more: > >   \* Is that partition mounted as one of the standard partitions (/usr...) or > something else? something else = prefix=/dmsp/reference/ we have tons of stuff living there >   \* Do you have to do anything on each of those 50 machines, or just mount > the NFS partition--hmm, I guess you'd at least have to add something to the > PATH of each user (at least, if a non-standard partition)? yes. PATH must be set. this is done in /etc/profile.d/dmsp.sh. we also set LD\_LIBRARY\_PATH here - thought this needed be done (see below) > I might try this, or even on a local non-standard partition (I guess I just > have to set the prefix appropriately). > > This might solve some problems for me--I'm trying to get TkHTML working for > me, and by now I'm concerned that I've tried so many things I've created more > problems for myself--I could start completely over on a new partition. exactly one of the issues i had! i have tcl/tk compiled and installed this way too. > Then I guess I'd have to do the ./configure --prefix=dst && make && sudo make > install process for: > > Ruby > tcltk (or ActiveTcl) > TkHTML (although in reading the instructions for this I realize there are some > special things to deal with, like the "parallel" bld directory) yup. > More info: > > Part of my problem is that I've compiled Ruby, then installed ActiveTcl, and I > don't know how to uninstall something that I installed by compiling. > ActiveTcl seemed to have an uninstall.tcl script, but that failed for me. I > guess I'll just go around and delete all files and directories that look like > they have anything to do with Ruby, tcltk, ActiveTcl, or TkHTML, and then > start over. > > This is on a Mandriva2006 system. I don't know whether the rpms on Mandriva > are to blame in any way--I suspect most of the problem(s) are just my > ignorance/inexperience in setting something like this up. if you follow these steps just about anything will work:    - chose a common nfs location. we'll call it /nfs    - every single time you compile something do this        export LD\_RUN\_PATH=/nfs/lib        export LD\_LIBRARY\_PATH=/nfs/lib        ./configure --prefix=/nfs && make && make install      i set LD\_LIBRARY\_PATH and LD\_RUN\_PATH in my .bashrc because i do this so      much. the cool thing with LD\_RUN\_PATH is that it \_\_encodes\_\_      inter-library dependancies (so ruby tk.so needs libtk.so needs ...) such      that users do not need to set LD\_LIBRARY\_PATH themselves. of course they      may, but they do not have to    - all users of code on this partiion need only do        export PATH=/nfs/bin:$PATH i have a /nfs/build and /nfs/packages - you can guess what these are for 😉 if you like this approach you may want to check out gnu stowe. i find it easy enough to do by hand though... regards. -a > **···** > > On Fri, 31 Mar 2006, Randy Kramer wrote: > > > On Thursday 30 March 2006 12:59 pm, ara.t.howard@noaa.gov wrote: > > -- > share your knowledge. it's a way to achieve immortality. > - h.h. the 14th dali lama ---
**Author:** ![Ryan\_Allen](https://avatars.discourse-cdn.com/v4/letter/r/43a26b/32.png) [@Ryan\_Allen](https://rubytalk.org/u/Ryan_Allen)\ **Post date:** [30 March 2006 23:58 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/7 "2006-03-30T23:58:16Z")
Hi Guys (and Gals!) This is my first post on the list, so Hello! Something very strange is happening (as far as I can tell) with a float comparison; here is the code in question: ("55.59".to\_f / 100) == 0.5559 # returns false However: "55.59".to\_f / 100 # returns Float 0.5559 0.5559 # returns Float 0.5559 0.5559 == 0.5559 # returns true And more!: ("55.5".to\_f / 100) == 0.555 # returns true ("55.53".to\_f / 100) == 0.5553 # returns true ("55.56".to\_f / 100) == 0.5556 # returns true ("55.58".to\_f / 100) == 0.5558 # returns true ("55.59".to\_f / 100) == 0.5559 # returns false !! ("44.59".to\_f / 100) == 0.4449 # returns true !! ("44.59".to\_f / 100) == 0.4449 # returns false !!!! It doesn't seem to like .59's... What did .59 ever do? I picked this up while writing a unit test, I've run this code in irb and I'm not sure what's going on... Can anyone shed some light on this? I'm using ruby 1.8.4 (2005-12-24) [powerpc-darwin8.5.0] Cheers, Ryan. ---
**Author:** ![Ara.T.Howard6](https://avatars.discourse-cdn.com/v4/letter/a/958977/32.png) [@Ara.T.Howard6](https://rubytalk.org/u/Ara.T.Howard6)\ **Post date:** [31 March 2006 00:12 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/8 "2006-03-31T00:12:47Z")
> I tried the suggestion of installing from source and I like the result > better. (My suggestion to run rdoc --ri is only useful if you run it > in some directory whose tree contains the source code (\*.c) files for > Ruby. ) After an install from source with > ../configure > make > su > make install great. > The ri and irb commands work fine. But when I try to use FxRuby, the > extension for the Fox Gui Toolkit, there are problems. The extension > wants the library libruby.so, which is missing. I tried > > make distclean > ../configure --enable-shared --enable-install-doc --enable-pthread > (As if I really knew what I was doing !) > make > make install-all > > Then I had a libruby.so and ruby, irb and ri still worked. > > However the elementary test > \> require 'fox14' > fails since it cannot find the files fox14/core.rb and fox14/core.so. > An strace of this process shows it is looking in the correct path for > the files. (I resorted to running irb in the fox14 directory.) The > problem is that the files were not produced when I compiled fox-1.4.32. here is what i think happened (largely guessing):    - you compiled ruby using defaults. this installed into --prefix=/usr/local      see if this is true. if so see what happens why you type        /usr/local/bin/irb      does it work? if so great. note that you still probably have another      ruby and irb in /usr/bin!    - now, rhe is evil and does not look in /usr/local/lib for linking. the way      to handle this is to configure the linker properly. do a 'man ldconfig'      or 'man ld.so' - basically you have to add a line with '/usr/local/lib' to      '/etc/ld.so.conf' and run 'ldconfig'. this just tells the system to look      here for libs. the reason you want to do this is because your libruby.so      is probably in /usr/local/lib/libruby.so now. (is it?)    - here is a totally general way to compile stuff, including stuff that has      mutual dependancies        export prefix=/usr/local/        export LD\_LIBRARY\_PATH=$prefix/lib        export LD\_RUN\_PATH=$prefix/lib        export PATH=$prefix/lib        ./configure --prefix=$prefix && make && sudo make install      (note: never, never, never compile as root)      if you build ruby this was and then fox all should be well. ping me      offline if you stil have issues. you can probably recover what you have      by setting the right ENV vars - but it may be easier to start over with      ruby first... maybe not. if you have issues ping me offline so we don't bore everyone... > I'll be delighted if someone can tell me the answer to that problem. > However to return to generalities: I think people trying to use Ruby > face more of a challenge than Perl and Python users since they are less > likely to find Ruby installed and ready-to-go. In the current epoch, > writers of tutorials would do better to give detailed coverage of > installation problems. Otherwise the pages about how easy and nice > Ruby is will seem a fraud. > > For example, if you read the typical exposition of the > require 'xyz' > "command, it doesn't explain how the name 'xyz' is connected to any > file on the machine. By experiment it seems to search for a directory > named 'xyz'. What paths does it take? What files does it need in that > directory? If everything is perfectly installed you don't have to > worry about this, but in practice you do. true statements all. like i said before though - the best (but painful) - answer (imho) is to learn about the compilers and linkers on your system. as lame as this sounds one can take solace in the fact that it's like learning 'vi' - once you know it you're set on \_\_any\_\_ \*nix system - including macs. btw. are you a sysad? we sure can't get root on ANY of our systems now unless one is a sysad... kind regards. -a > **···** > > On Fri, 31 Mar 2006 stephen.tashiro@us.army.mil wrote: > -- > share your knowledge. it's a way to achieve immortality. > - h.h. the 14th dali lama ---
**Author:** ![Mike\_Stok1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/mike_stok1/32/2065_2.png) [@Mike\_Stok1](https://rubytalk.org/u/Mike_Stok1)\ **Post date:** [31 March 2006 00:04 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/9 "2006-03-31T00:04:55Z")
You might want to look at [http://docs.sun.com/source/806-3568/ncg\_goldberg.html](http://docs.sun.com/source/806-3568/ncg_goldberg.html) and [http://support.microsoft.com/kb/q69333/](http://support.microsoft.com/kb/q69333/) ratdog:~ mike$ irb irb(main):001:0\> '%.40f' % 0.5559 =\> "0.5558999999999999497291014449729118496180" irb(main):002:0\> '%.40f' % (55.59 / 100) =\> "0.5559000000000000607514039074885658919811" irb(main):003:0\> '%.40f' % ("55.59".to\_f / 100) =\> "0.5559000000000000607514039074885658919811" Mike > **···** > > On 30-Mar-06, at 6:58 PM, Ryan Allen wrote: > > > Hi Guys (and Gals!) > > > > This is my first post on the list, so Hello! > > > > Something very strange is happening (as far as I can tell) with a float comparison; here is the code in question: > > > > ("55.59".to\_f / 100) == 0.5559 # returns false > > > > However: > > > > "55.59".to\_f / 100 # returns Float 0.5559 > > 0.5559 # returns Float 0.5559 > > 0.5559 == 0.5559 # returns true > > > > And more!: > > > > ("55.5".to\_f / 100) == 0.555 # returns true > > ("55.53".to\_f / 100) == 0.5553 # returns true > > ("55.56".to\_f / 100) == 0.5556 # returns true > > ("55.58".to\_f / 100) == 0.5558 # returns true > > ("55.59".to\_f / 100) == 0.5559 # returns false !! > > ("44.59".to\_f / 100) == 0.4449 # returns true !! > > ("44.59".to\_f / 100) == 0.4449 # returns false !!!! > > > > It doesn't seem to like .59's... What did .59 ever do? > > > > I picked this up while writing a unit test, I've run this code in irb and I'm not sure what's going on... > > > > Can anyone shed some light on this? > > > > I'm using ruby 1.8.4 (2005-12-24) [powerpc-darwin8.5.0] > > > > Cheers, > > Ryan. > > -- > > Mike Stok \ > [http://www.stok.ca/~mike/](http://www.stok.ca/~mike/) > > The "`Stok' disclaimers" apply. ---
**Author:** ![Matthew\_D\_Moss](https://avatars.discourse-cdn.com/v4/letter/m/b9e5f3/32.png) [@Matthew\_D\_Moss](https://rubytalk.org/u/Matthew_D_Moss)\ **Post date:** [31 March 2006 00:07 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/10 "2006-03-31T00:07:01Z")
> ("44.59".to\_f / 100) == 0.4449 # returns true !! > ("44.59".to\_f / 100) == 0.4449 # returns false !!!! Typos? You typed the same exact line twice and it comes back with two different answers? In any case, exact equality comparisons of floating-point numbers is bad. Don't do it. Either compare with a small threshold, or deal with rationals. ---
**Author:** ![Tim\_Hunter](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@Tim\_Hunter](https://rubytalk.org/u/Tim_Hunter)\ **Post date:** [31 March 2006 00:13 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/11 "2006-03-31T00:13:43Z")
Ryan Allen wrote: > Hi Guys (and Gals!) > > This is my first post on the list, so Hello! > > Something very strange is happening (as far as I can tell) with a float comparison; here is the code in question: > > ("55.59".to\_f / 100) == 0.5559 # returns false > > However: > > "55.59".to\_f / 100 # returns Float 0.5559 > 0.5559 # returns Float 0.5559 > 0.5559 == 0.5559 # returns true > > And more!: > > ("55.5".to\_f / 100) == 0.555 # returns true > ("55.53".to\_f / 100) == 0.5553 # returns true > ("55.56".to\_f / 100) == 0.5556 # returns true > ("55.58".to\_f / 100) == 0.5558 # returns true > ("55.59".to\_f / 100) == 0.5559 # returns false !! > ("44.59".to\_f / 100) == 0.4449 # returns true !! > ("44.59".to\_f / 100) == 0.4449 # returns false !!!! > > It doesn't seem to like .59's... What did .59 ever do? > > I picked this up while writing a unit test, I've run this code in irb and I'm not sure what's going on... > > Can anyone shed some light on this? > > I'm using ruby 1.8.4 (2005-12-24) [powerpc-darwin8.5.0] > > Cheers, > Ryan. The comparison of floating-point numbers is notoriously problematic throughout all computing, not just Ruby. Here's a good description of the problem: [http://en.wikipedia.org/wiki/Floating\_point\](http://en.wikipedia.org/wiki/Floating_point%5C). You can also find many discussions of this same "problem" by searching the archives of this list. Typically you don't test two floating-point numbers for equality, you test that the difference is very small. This is what the assert\_in\_delta assertion is for. ---
**Author:** ![Thomas\_E\_Enebo](https://avatars.discourse-cdn.com/v4/letter/t/82dd89/32.png) [@Thomas\_E\_Enebo](https://rubytalk.org/u/Thomas_E_Enebo)\ **Post date:** [31 March 2006 00:13 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/12 "2006-03-31T00:13:52Z")
On Fri, 31 Mar 2006, Ryan Allen defenestrated me: > Hi Guys (and Gals!) > > This is my first post on the list, so Hello! > > Something very strange is happening (as far as I can tell) with a > float comparison; here is the code in question: > > ("55.59".to\_f / 100) == 0.5559 # returns false > > It doesn't seem to like .59's... What did .59 ever do? > > I picked this up while writing a unit test, I've run this code in irb > and I'm not sure what's going on... > > Can anyone shed some light on this?   Looking at some IEEE spec will explain this in agonizing detail, but simply stated numbers in a computer are stored in a base 2 format. The math you are doing is base 10. Not all base 10 values can be perfectly represented in base 2. This can cause calculations to not quite come out right.   A book on numerical analysis can also be a good intro on this stuff. -Tom > **···** > > -- > + [http://www.tc.umn.edu/~enebo](http://www.tc.umn.edu/~enebo) +---- [mailto:enebo@acm](mailto:enebo@acm).org ----+ > > > Thomas E Enebo, Protagonist | "Luck favors the prepared | > >                              \> mind." -Louis Pasteur | ---
**Author:** ![List\_Recv](https://avatars.discourse-cdn.com/v4/letter/l/dec6dc/32.png) [@List\_Recv](https://rubytalk.org/u/List_Recv)\ **Post date:** [31 March 2006 04:03 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/13 "2006-03-31T04:03:44Z")
Just to corroborate: I actually do prefer RHEL distros, but the Ruby RPM's should be avoided. ---
**Author:** ![Randy\_Kramer](https://avatars.discourse-cdn.com/v4/letter/r/dbc845/32.png) [@Randy\_Kramer](https://rubytalk.org/u/Randy_Kramer)\ **Post date:** [31 March 2006 15:47 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/14 "2006-03-31T15:47:58Z")
Thanks very much! I haven't tried this yet, but it looks like it should solve a lot of my problems. Randy Kramer > **···** > > On Thursday 30 March 2006 05:21 pm, ara.t.howard@noaa.gov wrote: > > > On Fri, 31 Mar 2006, Randy Kramer wrote: > > \> On Thursday 30 March 2006 12:59 pm, ara.t.howard@noaa.gov wrote: > > if you follow these steps just about anything will work: > > > >    - chose a common nfs location. we'll call it /nfs > > > >    - every single time you compile something do this > > > >        export LD\_RUN\_PATH=/nfs/lib > >        export LD\_LIBRARY\_PATH=/nfs/lib > >        ./configure --prefix=/nfs && make && make install > > > >      i set LD\_LIBRARY\_PATH and LD\_RUN\_PATH in my .bashrc because i do this > > so much. the cool thing with LD\_RUN\_PATH is that it \_\_encodes\_\_ > > inter-library dependancies (so ruby tk.so needs libtk.so needs ...) such > > that users do not need to set LD\_LIBRARY\_PATH themselves. of course they > > may, but they do not have to > > > >    - all users of code on this partiion need only do > > > >        export PATH=/nfs/bin:$PATH > > > > i have a /nfs/build and /nfs/packages - you can guess what these are for > > 😉 if you like this approach you may want to check out gnu stowe. i find > > it easy enough to do by hand though... ---
**Author:** ![Ryan\_Allen](https://avatars.discourse-cdn.com/v4/letter/r/43a26b/32.png) [@Ryan\_Allen](https://rubytalk.org/u/Ryan_Allen)\ **Post date:** [31 March 2006 00:29 UTC](https://rubytalk.org/t/unintentional-hype-of-ruby-irb-and-ri/26253/15 "2006-03-31T00:29:05Z")
Thank you for the replies! I should have searched the list first before asking! Ryan.