Bug in date.rb?

ruby-talk
1

Hello

I have found following statement in date.rb:
def <=> (other)
case other
when Numeric; return @ajd <=> other
when Date; return @ajd <=> other.ajd
end
raise TypeError, 'expected numeric or date’
end

So I can’t compare a date with nil, because I get an error. Instead I
have to write something like date.instance_of? NilClass, which is
something unnecessary complicated.

Why is this implemented this way?

···

–
Marek Janukowicz

2

Hi,

···

In message “Bug in date.rb?” on 03/03/03, Child child@t9.ds.pwr.wroc.pl writes:

So I can’t compare a date with nil, because I get an error. Instead I
have to write something like date.instance_of? NilClass, which is
something unnecessary complicated.

Why is this implemented this way?

Why do you want to compare date with nil, when nil <=> date raises
NoMethodError? Although it is better complied to other part of Ruby,
if it returns nil instead of raising exception.

						matz.
3

Child child@t9.ds.pwr.wroc.pl writes:

So I can’t compare a date with nil, because I get an error. Instead I
have to write something like date.instance_of? NilClass, which is
something unnecessary complicated.

Try:

date.nil?
···

–
matt

4

Hi,

I have found following statement in date.rb:
def <=> (other)
case other
when Numeric; return @ajd <=> other
when Date; return @ajd <=> other.ajd
end
raise TypeError, ‘expected numeric or date’
end

Try newer version.

def <=> (other)
case other
when Numeric; return @ajd <=> other
when Date; return @ajd <=> other.ajd
end
nil
end

						matz.
···

In message “Bug in date.rb?” on 03/10/11, Child child@t9.ds.pwr.wroc.pl writes:

5

Because in this specific case I don’t know whether this variable is
uninitialized (nil) or is a Date or something else. I write a database
library and I check if the values I am inserting are not null. If they
aren’t, the only data type I have problem with is Date, because I can’t
compare it with nil.

···

On Mon, 3 Mar 2003 11:14:21 +0900, Yukihiro Matsumoto wrote:

So I can’t compare a date with nil, because I get an error. Instead I
have to write something like date.instance_of? NilClass, which is
something unnecessary complicated.

Why is this implemented this way?

Why do you want to compare date with nil, when nil <=> date raises
NoMethodError? Although it is better complied to other part of Ruby,
if it returns nil instead of raising exception.

–
Marek Janukowicz

6

I didn’t know this method - thanks!

···

On Tue, 4 Mar 2003 01:07:03 +0900, Matt Armstrong wrote:

So I can’t compare a date with nil, because I get an error. Instead I
have to write something like date.instance_of? NilClass, which is
something unnecessary complicated.
Try:

date.nil?

–
Marek Janukowicz

7

I think that if foo <=> nil returned nil, it would have a number of
important and possibly undesirable knock-on effects. For example, what would
'sort' do when spaceship returns nil? Would foo < nil also end up returning
nil? What would happen if you tried to compare two other non-comparable
classes, e.g. 3 <=> true ?

You might find that one of the following patterns achieves what you want
without too much difficultly:

  <do something> unless foo.nil? # shorter than 'foo.instance_of? NilClass'
  
  foo ||= SomeDefaultValue # only assigns if foo==nil or false

Or you could use begin...rescue...end around the code section.

Regards,

Brian.

···

On Mon, Mar 03, 2003 at 06:15:18PM +0900, Child wrote:

On Mon, 3 Mar 2003 11:14:21 +0900, Yukihiro Matsumoto wrote:
>>So I can't compare a date with nil, because I get an error. Instead I
>>have to write something like date.instance_of? NilClass, which is
>>something unnecessary complicated.
>>
>>Why is this implemented this way?
>
> Why do you want to compare date with nil, when nil <=> date raises
> NoMethodError? Although it is better complied to other part of Ruby,
> if it returns nil instead of raising exception.

Because in this specific case I don't know whether this variable is
uninitialized (nil) or is a Date or something else. I write a database
library and I check if the values I am inserting are not null. If they
aren't, the only data type I have problem with is Date, because I can't
compare it with nil.

8

i often use

eg.

user = ENV[‘USER’]
comment = ‘foobar’
date = nil

statements = <<-sql
insert into
mytable
values ( #{user}, #{comment}, #{date or Time.now} )
sql

conn.exec statements

but better still

create table mytable
(
user text,
comment text,
date timestamp default now()
)

since this will handle ‘nil’ values from ruby, perl, c, sql-command prompt,
etc.

IMHO: if there is the notion of a ‘default’ date for your schema, it should be
represented in the schema - not ruby code. if there is not, the TypeError
raised should halt the program so date <=> nil need not be changed. of
course, this is not always feasible but i thought i’d mention it…

-a

···

On Mon, 3 Mar 2003, Brian Candler wrote:

You might find that one of the following patterns achieves what you want
without too much difficultly:

unless foo.nil? # shorter than ‘foo.instance_of? NilClass’

foo ||= SomeDefaultValue # only assigns if foo==nil or false

Or you could use begin…rescue…end around the code section.

–

Ara Howard
NOAA Forecast Systems Laboratory
Information and Technology Services
Data Systems Group
R/FST 325 Broadway
Boulder, CO 80305-3328
Email: ahoward@fsl.noaa.gov
Phone: 303-497-7238
Fax: 303-497-7259
====================================