From: Robert Kedoin <robert@...>
Date: 2001-05-17T01:44:06+09:00
Subject: [ruby-talk:15299] Q: Should initializers validate arguments ?

I'm new to Ruby and I came across something today and I was wondering if 
it's a bug or a philosophical issue.

In Ruby 1.6.3, it is possible to create a Range object with two Time 
object's as start and end. However, since Time does not respond to 
#succ, when you try to send most methods to the Range you fail since 
#each cannot work.

I would have expected that I would have gotten some sort of exception 
when I created the Range.

Similarly, it is possible to create a Range with a start and and end 
that are of completely different classes. Again this doesn't generate 
any error at creation time, but fails to do anything meaningful later.

Is it a design decision not to check the fitness of these arguments and 
wait until later to find out if the Range is valid. Or are they bugs ?

Below is some code that demonstrates what I'm talking about.

Robert Kedoin

p.s I've since found the Date class which did what I wanted, but I was 
still confused about the behavior I was seeing...
	-Rob

--- cut here ---
#!/usr/bin/env ruby
#
# experiment with using Time in a range
require 'date'

thisYear = Time.now.year

now = Time.now
today = Time.local(now.year,now.month,now.day)

# Create a range of Time's for the month of May
puts "Creating a range of Time"
may = Time.local(thisYear,5,1)..Time.local(thisYear,5,30)
#-> I would have expected an error here since Time doesn't support #succ

begin
#  puts "range length is #{may.length}"
   puts may.include?(today)
rescue NameError
   $stderr.puts "Range operation failed:" + $!
end

# Simlarly it is possible to create a range with two completely unrelated
# classes
puts "\nCreating a range from Date to Fixnum"
may = Date.new(thisYear,5,1)..5

#-> I would have expected an error here since although Date and Fixnum 
support
# #succ, it probably isn't meaningful to count from one to the other
puts may.to_a
puts "Range length is #{may.length}"

# Interestingly enough, reversing the Fixnum and Date *does* generate an
# error when creating the Range
puts "\nCreating a range from Fixnum to Date"
may = 5..Date.new(thisYear,5,1)