If you've ever read "Real Programmers don't use Pascal" (see
Real Programmers Don't Use PASCAL - CodeProject ) you'll know that
"Determined Real Programemrs can write Fortran programs in any language"
Just because you're a Ruby programmer you don't have to use all that OO
stuff.
That's true. However, I would add that the choice of language does not determine the algorithm to use nor how it is implemented. We'll come to that in a minute.
This algorithm picks out the first label and moves it into a new space
on the left, and then moves the second label to where the first was and
so on. Lastly it removes the vacated slot on the right:
Here we see the first indication of a bad implementation: the number of labels is encoded in the algorithm. You cannot use that program with other than three labels. Even worse, the exact labels are hard coded into the program. In other words, your program is overly dependent on the input, or - put differently - your program is not very general and poses too many restrictions on the input.
def initialise_globals
$m1 = "JANUARY"
$m2 = "FEBRUARY"
$m3 = "MARCH"
$m1_index = 0
$m2_index = 0
$m3_index = 0
end
Others have commented on the use of global variables already.
def get_array
$input_array = ["#<Event:0x4d4cf78>", "#<Event:0x4d4d470>", "MARCH",
"#<Event:0x4d4dc08>",
"#<Event:0x4d4e100>", "FEBRUARY", "#<Event:0x4d4e898>","JANUARY"]
puts " #{$input_array}"
end
def shuffle_all_right
#insert m3 while we’re at it.
$input_array.unshift " "
end
Isn't this "OO stuff" that you did not want to use?
def locate_months
$m1_index = $input_array.index $m1
$m2_index = $input_array.index $m2
$m3_index = $input_array.index $m3
end
Here you are clearly cheating: you use "all that OO stuff". Even worse, by using Array#index you are hiding the fact that you traverse the input Array far more often than necessary.
def bring_months_to_left
$input_array[0] = $input_array[$m3_index]
$input_array[$m3_index] = $input_array[$m2_index]
$input_array[$m2_index] = $input_array[$m1_index]
end
def delete_right_slot
$input_array.pop
end
Again, "OO stuff".
def main_program
initialise_globals
get_array
shuffle_all_right
locate_months
bring_months_to_left
delete_right_slot
end
main_program
puts $input_array
Actually I cheated there as I enclosed the #strings in quotes. Anyone
know how to deal with #s?
If you want to make the point that using Ruby does not necessitate the usage of "all this OO stuff" a better program (i.e. one that at least avoids issues raised so far) would certainly have given your argument more strength.
I believe the program I wrote whilst not typical of Ruby programs is
quicker to understand than the more dense solutions given by others -
and that's important in programming.
Well, then compare that to the version below. I claim that it uses (mostly) procedural style and yet is easier to read and understand than your version.
# test whether the given element is a month label
def is_label(o)
String === o
end
# exchange values at positions
def swap(arr, i, j)
# not using parrallel assignment since
# we want to avoid all the fancy stuff
x = arr[i]
arr[i] = arr[j]
arr[j] = x
end
# Input: array with Events followed by month
# Output: number of events without month at end
# Side effect: months precede their Events
def realign_months(arr)
start = 0
i = 0
while i < arr.length
if is_label(arr[i])
# swap label and first
swap(arr, i, start)
# remember begin of next section
start = i + 1
end
i += 1
end
# remaining elements without month
return arr.length - start
end
# we add a field only for easier reading of output
Event = Struct.new :no
arr = [
Event.new(1),
Event.new(2),
Event.new(3),
"January",
Event.new(4),
"February",
Event.new(5),
Event.new(6),
Event.new(7),
"March",
Event.new(8),
Event.new(9),
"April",
]
p arr
remainder = realign_months(arr)
p arr
if remainder > 0
$stderr.puts "Last #{remainder} events are misaligned"
end
I would readily admit that it does not exactly do the same thing as your program. You can find this version and a version that maintains original element ordering (such as your version does) here: Change order of elements so labels precede their values · GitHub
Kind regards
robert
···
On 01.12.2010 19:30, Mike Stephens wrote:
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
4> results << 