Bug #7083: Why I cannot pass the test?

• Status: Third Party's Issue
• Assignee: -
• Target version: -
• ruby -v: ruby 1.9.3p194 (2012-04-20) [i386-mingw32]

[mghomn (Justin Peal)]

=== Program ===
#!/usr/bin/env ruby -w

encoding: utf-8

require 'test/unit'

class Currency
attr_reader :currency, :decimal_digits

def initialize currency, decimal_digits
@currency, @decimal_digits = currency, decimal_digits
end
end

class Money
attr_reader :hashy

def initialize hashy
@hashy = hashy
clean()
end

def == other
@hashy == other.hashy
end

def -@
@hashy.each_pair do |currency, amount|
@hashy[currency] = -amount
end
clean()
end

def + other
@hashy.merge!(other.hashy) do |currency, old_amount, new_amount|
old_amount.to_f + new_amount.to_f
end
clean()
end

def - other
@hashy.merge!(other.hashy) do |currency, old_amount, new_amount|
old_amount.to_f - new_amount.to_f
end
clean()
end

def * times
@hashy.each_pair do |currency, amount|
@hashy[currency] *= times
end
clean()
end

def / times
@hashy.each_pair do |currency, amount|
@hashy[currency] /= times
end
clean()
end

def clean
@hashy.each_pair do |currency, amount|
amount_new = amount.to_f.round(currency.decimal_digits)
case
when amount_new == 0.0
@hashy.delete(currency)
when amount_new != amount
@hashy[currency] = amount_new
end
end
self
end
end

class MoneyTest < Test::Unit::TestCase
def test_add
usd = Currency.new(:USD, 2)
cny = Currency.new(:CNY, 2)
eur = Currency.new(:EUR, 2)
jpy = Currency.new(:JPY, 0)
gbp = Currency.new(:GBP, 2)

assert_equal(Money.new(eur=>367.85, cny=>-337.19, jpy=>42289), Money.new(eur=>867.02, cny=>-794.75, jpy=>99675) / 2.357)
assert_equal(Money.new(cny=>1576.56, gbp=>752.26, jpy=>64174), Money.new(cny=>861.51, gbp=>411.07, jpy=>35068) * 1.83)
assert_equal(Money.new(usd=>367.04, cny=>418.27, eur=>728.18), Money.new(cny=>418.27, usd=>129.66) + Money.new(usd=>237.38, eur=>728.18))
assert_equal(Money.new(eur=>211.32, cny=>-980.95, jpy=>31647), -Money.new(eur=>-211.32, cny=>980.95, jpy=>-31647))
assert_equal(Money.new(jpy=>19627, usd=>442.39, gbp=>-393.84), Money.new(jpy=>19627, usd=>908.64) - Money.new(usd=>466.25, gbp=>393.84))

end
end
=== Result ===
Run options:

Running tests:

F

Finished tests in 0.029999s, 33.3344 tests/s, 166.6722 assertions/s.

1. Failure:
   test_add(MoneyTest) [C:/R/tst2.rb:87]:
   <#<Money:0x1b463f8
   @hashy=
   {#<Currency:0x1b56148 @currency=:JPY, @decimal_digits=0>=>19627,
   #<Currency:0x1b561f0 @currency=:USD, @decimal_digits=2>=>442.39,
   #<Currency:0x1b560b8 @currency=:GBP, @decimal_digits=2>=>-393.84}>> expected
   but was
   <#<Money:0x1b462f0
   @hashy=
   {#<Currency:0x1b56148 @currency=:JPY, @decimal_digits=0>=>19627,
   #<Currency:0x1b561f0 @currency=:USD, @decimal_digits=2>=>442.39,
   #<Currency:0x1b560b8 @currency=:GBP, @decimal_digits=2>=>393.84}>>.

1 tests, 5 assertions, 1 failures, 0 errors, 0 skips

[phluid61 (Matthew Kerwin)]

On 29 September 2012 16:55, mghomn (Justin Peal) [e-mail] wrote:

Issue #7083 has been reported by mghomn (Justin Peal).

---

Bug #7083: Why I cannot pass the test?
https://bugs.ruby-lang.org/issues/7083

Author: mghomn (Justin Peal)
Status: Open
Priority: Normal
Assignee:
Category:
Target version:
ruby -v: ruby 1.9.3p194 (2012-04-20) [i386-mingw32]

=== Program ===
#!/usr/bin/env ruby -w

encoding: utf-8

require 'test/unit'

class Currency
attr_reader :currency, :decimal_digits

def initialize currency, decimal_digits
@currency, @decimal_digits = currency, decimal_digits
end
end

class Money
attr_reader :hashy

def initialize hashy
@hashy = hashy
clean()
end

def == other
@hashy == other.hashy
end

def -@
@hashy.each_pair do |currency, amount|
@hashy[currency] = -amount
end
clean()
end

def + other
@hashy.merge!(other.hashy) do |currency, old_amount, new_amount|
old_amount.to_f + new_amount.to_f
end
clean()
end

def - other
@hashy.merge!(other.hashy) do |currency, old_amount, new_amount|
old_amount.to_f - new_amount.to_f
end
clean()
end

def * times
@hashy.each_pair do |currency, amount|
@hashy[currency] *= times
end
clean()
end

def / times
@hashy.each_pair do |currency, amount|
@hashy[currency] /= times
end
clean()
end

def clean
@hashy.each_pair do |currency, amount|
amount_new = amount.to_f.round(currency.decimal_digits)
case
when amount_new == 0.0
@hashy.delete(currency)
when amount_new != amount
@hashy[currency] = amount_new
end
end
self
end
end

class MoneyTest < Test::Unit::TestCase
def test_add
usd = Currency.new(:USD, 2)
cny = Currency.new(:CNY, 2)
eur = Currency.new(:EUR, 2)
jpy = Currency.new(:JPY, 0)
gbp = Currency.new(:GBP, 2)

assert_equal(Money.new(eur=>367.85, cny=>-337.19, jpy=>42289), Money.new(eur=>867.02, cny=>-794.75, jpy=>99675) / 2.357)
assert_equal(Money.new(cny=>1576.56, gbp=>752.26, jpy=>64174), Money.new(cny=>861.51, gbp=>411.07, jpy=>35068) * 1.83)
assert_equal(Money.new(usd=>367.04, cny=>418.27, eur=>728.18), Money.new(cny=>418.27, usd=>129.66) + Money.new(usd=>237.38, eur=>728.18))
assert_equal(Money.new(eur=>211.32, cny=>-980.95, jpy=>31647), -Money.new(eur=>-211.32, cny=>980.95, jpy=>-31647))
assert_equal(Money.new(jpy=>19627, usd=>442.39, gbp=>-393.84), Money.new(jpy=>19627, usd=>908.64) - Money.new(usd=>466.25, gbp=>393.84))

end
end
=== Result ===
Run options:

Running tests:

F

Finished tests in 0.029999s, 33.3344 tests/s, 166.6722 assertions/s.

1. Failure:
   test_add(MoneyTest) [C:/R/tst2.rb:87]:
   <#<Money:0x1b463f8
   @hashy=
   {#<Currency:0x1b56148 @currency=:JPY, @decimal_digits=0>=>19627,
   #<Currency:0x1b561f0 @currency=:USD, @decimal_digits=2>=>442.39,
   #<Currency:0x1b560b8 @currency=:GBP, @decimal_digits=2>=>-393.84}>> expected
   but was
   <#<Money:0x1b462f0
   @hashy=
   {#<Currency:0x1b56148 @currency=:JPY, @decimal_digits=0>=>19627,
   #<Currency:0x1b561f0 @currency=:USD, @decimal_digits=2>=>442.39,
   #<Currency:0x1b560b8 @currency=:GBP, @decimal_digits=2>=>393.84}>>.

1 tests, 5 assertions, 1 failures, 0 errors, 0 skips

It appears from my reading of the documentation that Hash#merge /
#merge! only runs the block when resolving duplicate keys. This is
borne out by a simply check in IRB:

irb(main):004:0> {}.merge( {:a=>3} ){|a,b,c| p [a,b,c]; b-c }
=> {:a=>3}
irb(main):005:0> {b:1}.merge( {:a=>3} ){|a,b,c| p [a,b,c]; b-c }
=> {:b=>1, :a=>3}
irb(main):006:0> {a:6, b:1}.merge( {:a=>3} ){|a,b,c| p [a,b,c]; b-c }
[:a, 6, 3]
=> {:a=>3, :b=>1}

If I were to attempt to mend this I'd start with a less graceful
solution, like replacing the #- method with something like*:

def - other
self + (-(Money.new other.hashy.dup))
end

It's a bit uglier than it could otherwise be, but all the operations
are bangy (i.e. they modify the receiving object) so I can't just use:
self + (-other), and the constructor doesn't copy the inital hash.

The multiplication operation is even weirder; I'm not sure whether
{usd=>1} * {gbp=>2} should result in {usd=>1,gbp=>2} (which it
currently does) or {usd=>0,gbp=>0} (which seems to be implied by your
interpretation of the subtraction operation). Of course this makes
division even more weirderer, since you have potential
division-by-zero issues to resolve.

• no code in this post was actually tested by me

--
Matthew Kerwin, B.Sc (CompSci) (Hons)
http://matthew.kerwin.net.au/
ABN: 59-013-727-651

"You'll never find a programming language that frees
you from the burden of clarifying your ideas." - xkcd

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Third Party's Issue

[mghomn (Justin Peal)]

You are awsome!