Built-in vs. standard library

Ruby
1

I’m confused about whether the Date class is built-in or in the
standard library.

I can use it without requiring it in irb, so that tells me it’s
built-in.
Pickaxe doesn’t document it in the “Built-in Classes and Modules”
reference chapter.
Pickaxe does document a Date class in the “Standard Library” chapter.
Are there two different date classes?
Should I be able to determine this by looking at source files under
the lib/ruby/1.8 directory?
It’s seems like those source files are all for standard library classes.
True?

2

On Feb 4, 2006, at 2:57 PM, Mark V. wrote:

I’m confused about whether the Date class is built-in or in the
standard library.

It’s a standard library.

I can use it without requiring it in irb, so that tells me it’s
built-in.

Na, that tells you that irb requires it somewhere. :slight_smile:

James Edward G. II

3

On 2/4/06, James Edward G. II [email protected] wrote:

Na, that tells you that irb requires it somewhere. :slight_smile:

Actually, it’s a little weirder than that. I’ve wondered about it
myself:

irb(main):001:0> Date.methods(false)
=> [“zone_to_diff”, “_parse”, “_strptime”]
irb(main):002:0> Date.today
NoMethodError: undefined method `today’ for Date:Class
from (irb):2
irb(main):003:0> require ‘date’
=> true
irb(main):004:0> Date.today
=> #<Date: 4907541/2,0,2299161>
irb(main):005:0> Date.methods(false)
=> [“jd_to_ajd”, “ld_to_jd”, “ordinal”, “ajd_to_amjd”, “new0”, “jd”,
“valid_ordinal?”, “exist2?”, “e
xist?”, “jd_to_civil”, “jd_to_wday”, “gregorian_leap?”,
“valid_commercial?”, “parse”, “new3”, “os?”,
“commercial_to_jd”, “jd_to_mjd”, “valid_civil?”, “new”,
“zone_to_diff”, “jd_to_ordinal”, "valid_jd?
", “commercial”, “exist1?”, “day_fraction_to_time”, “jd_to_ld”,
“julian_leap?”, “today”, “new2”, “_p
arse”, “existw?”, “ordinal_to_jd”, “amjd_to_ajd”, “ns?”,
“civil_to_jd”, “ajd_to_jd”, “valid_date?”,
“new1”, “_strptime”, “jd_to_commercial”, “mjd_to_jd”, “strptime”,
“exist3?”, “time_to_day_fraction”,
“leap?”, “civil”, “_load”, “neww”]
irb(main):006:0>

4

On 2/4/06, James Edward G. II [email protected] wrote:

Na, that tells you that irb requires it somewhere. :slight_smile:
Then why does this code run?

d = Date.new
puts “d is a #{d.class}”

This is telling me that there is a built-in Date class and there is
another one in the Standard Library.

ruby-doc.org documents a Date class under both the “Core API” and the
“Standard API”. They look very similar, but not identical. As I said
earlier, pickaxe does not document it as a built-in.

Why do there seem to be two Date classes?

5

On Sat, 04 Feb 2006 23:23:36 -0000, Mark V.
[email protected] wrote:

Na, that tells you that irb requires it somewhere. :slight_smile:

Then why does this code run?

d = Date.new
puts “d is a #{d.class}”

This is telling me that there is a built-in Date class and there is
another one in the Standard Library.

Just curious, what is your output from this code?

p 1 if defined? Date
require 'irb'
p 2 if defined? Date
require 'rubygems'
p 3 if defined? Date

I just get 3 (which I think is expected). Do you require rubygems in
your
…irbrc? or $RUBYOPTS?

6

Mark V. wrote:

R. Mark V.
Partner, Object Computing, Inc.

Hi,

I wonder if you might have required rubygems at some point. Sifting
through rubygems:
rubygems/open-uri.rb: require ‘parsedate’
parsedate.rb: require ‘date/format’

So if you’ve got RUBYOPT set to rubygems, you’ll have required rubygems
already. Try evaluating Date::MONTHNAMES. This constant is set in
date.rb and not date/format.rb so if you’ve only required data/format
then you’ll have a chance to hear the uninitialized constant song.

Having required rubygems would explain the presence of the Date class in
your ruby above.

Hope that helps. If anyone has a better idea of where the rogue Date
might be coming from, I’d love to hear it.

Regards,
Matthew J. Desmarais

P.S. I just realized that you’ll get a good idea of what (aside from
core) is in your ruby by evaluating $". That’s the array that holds the
list of files that have been require’d.

7

On 2/4/06, Ross B. [email protected] wrote:

This is telling me that there is a built-in Date class and there is
another one in the Standard Library.

Just curious, what is your output from this code?

    p 1 if defined? Date
    require 'irb'
    p 2 if defined? Date
    require 'rubygems'
    p 3 if defined? Date

I get
1
2
3

I just get 3 (which I think is expected). Do you require rubygems in your
…irbrc? or $RUBYOPTS?

I’m running Ruby 1.8.4 under Windows XP. I don’t have a RUBYOPTS
environment variable set and I get the result above when I put the
code in a file and run it with “ruby myfile.rb”, so I guess the .irbrc
part doesn’t matter.

8

Mark V. wrote:

that automatically happens when you are using the latest version of
the Windows One Click Installer? As was suggested earlier,
rubygems.rb ends up requiring parsedate.rb.

Very odd. I noticed that earlier in the thread that you said that you
didn’t have a RUBYOPTS environment variable set. The environment
variable that will get you is actually RUBYOPT. Is it possible that you
have this one set? If not then you can color me puzzled.

This still leaves the question of why ruby-doc.org documents the Date
class as being in the Core API.

Oh, that? I have no idea. :wink:

It probably shouldn’t be though, eh?

9

On 2/4/06, Matthew D. [email protected] wrote:

that automatically happens when you are using the latest version of
the Windows One Click Installer? As was suggested earlier,
rubygems.rb ends up requiring parsedate.rb.

Very odd. I noticed that earlier in the thread that you said that you
didn’t have a RUBYOPTS environment variable set. The environment
variable that will get you is actually RUBYOPT. Is it possible that you
have this one set? If not then you can color me puzzled.

Oops! You can color me red. I do have RUBYOPT set and it’s set to
rubygems. So that explains why the Date class is available without me
requiring it.

This still leaves the question of why ruby-doc.org documents the Date
class as being in the Core API.

Oh, that? I have no idea. :wink:

It probably shouldn’t be though, eh?

Right.

10

On 2/4/06, Matthew D. [email protected] wrote:

P.S. I just realized that you’ll get a good idea of what (aside from
core) is in your ruby by evaluating $". That’s the array that holds the
list of files that have been require’d.

Good suggestion! I tried that and I see that “rubygems.rb” is being
loaded. I just don’t know why that is happening. Is that something
that automatically happens when you are using the latest version of
the Windows One Click Installer? As was suggested earlier,
rubygems.rb ends up requiring parsedate.rb.

This still leaves the question of why ruby-doc.org documents the Date
class as being in the Core API.

11

Mark V. wrote:

that automatically happens when you are using the latest version of
the Windows One Click Installer? As was suggested earlier,
rubygems.rb ends up requiring parsedate.rb.

This still leaves the question of why ruby-doc.org documents the Date
class as being in the Core API.

Because I run rdoc over the base set of lib files.

If there is a better way to do this, I would be happy to change.

(What I would prefer is a single set of API files that do not require
one to know whether something is ‘core’ or ‘std-lib’. )

James

James B.

“The greatest obstacle to discovery is not ignorance, but the illusion
of knowledge.”

  • D. Boorstin