Gavin Sinclair
10/24/2003 7:57:00 AM
Hi -talk,
I'm having trouble dealing with a block that yields one parameter but
declares two. I've pasted complete test code below. Basically, I've
defined "sum" on Enumerable that sums the result of yielding each value.
This is for demonstration of the problem only.
When I define it like this
def sum
result = 0
self.each { |elt| result += yield(elt) }
result
end
{1=>2}.sum { |k,v| v } works but gives a warning.
[[1,2]].sum { |a,b| b } is fine.
When I define it like this
def sum
result = 0
self.each { |*elt| result += yield(*elt) }
result
end
{1=>2}.sum { |k,v| v } is fine.
[[1,2]].sum { |a,b| b } gives an error.
Below are the two definitions and a complete test case. In the test case,
the range examples have no problems so are uncommented. Comments are
given in the other cases.
I would really like to avoid the warning associated with the hash in
test_sum1h.
Thanks for any advice,
Gavin
--------------------------------------------------------------------------
module Enumerable
#
# Yield each element and return the (strictly numerical) sum of the
# results. sum1 and sum2 are different implementations.
#
def sum1
result = 0
self.each do |elt|
result += yield(elt)
end
result
end
def sum2
result = 0
self.each do |*elt|
result += yield(*elt)
end
result
end
end
require 'test/unit'
#
# Test case: set up 3 enumerable objects, and try sum1 and sum2 on
# each of them.
#
class TC_Sum < Test::Unit::TestCase
def setup
@r = (1..10) # We'll sum the squares (385)
@a = [ [1,2], [3,4], [5,6] ] # We'll sum the products (44)
@h = { :a => 1, :b => 2, :c => 3 } # We'll sum the values (6)
end
# ======== First implementation
def test_sum1r
puts "test_sum1r"
sum = @r.sum1 { |x| x ** 2 }
assert_equal(385, sum)
end
def test_sum1a
puts "test_sum1a"
sum = @a.sum1 { |x,y| x * y } # Passes.
assert_equal(44, sum)
end
def test_sum1h
puts "test_sum1h"
sum = @h.sum1 { |k,v| v } # Passes, with warning:
assert_equal(6, sum) # multiple values for a block
end # parameter (2 for 1)
# ======== Second implementation
def test_sum2r
puts "test_sum2r"
sum = @r.sum2 { |x| x ** 2 }
assert_equal(385, sum)
end
def test_sum2a
puts "test_sum2a"
sum = @a.sum2 { |x,y| x * y } # Error: no implicit conversion
assert_equal(44, sum) # from nil to integer
end
def test_sum2h
puts "test_sum2h"
sum = @h.sum2 { |k,v| v } # Passes.
assert_equal(6, sum)
end
end