Help please Undefined Method error

Hi and thank you for reading this
well im new at programming and ruby is the first language I’m trying to
learn so I’m really a newbie, I have this code wich I attached that
gives me this error

"C:/sort.rb:13:in sort': undefined method<’ for [“hello”, “loop”,
“array”, “teeth”, “wave”, “new”]:Array (NoMethodError)
from C:/sort.rb:29:in `’

So my question is: is there a way to make the main methods or ruby
premade methods like “<” “<=” “>” “>=” to work inside mi own method or
to call them or to define them again???

cause if I take it out of my metod “sort” it runs perfectly

Please anwer my question even if the code can be done in some other way
I whould really apreciate it it’s not just for this code but to know for
further use
Thanks and sorry if i’m bothering you with this newbie
question

words is an array, but you put it inside another array when you call
sort
just pass words
same for sorted

cheers

Oh thats right thank you very much

But there is another error in this code that is basically the same but
corrected in some things
so this is the error

[code]
sort_cor.rb:13:in <': comparison of String with nil failed (ArgumentError) from C:/sort_cor.rb:13:insort’
from C:/sort_cor.rb:30:in `’

[code]
and I don’t understand why is giving me nil

The program is done !!! i was only checking it for the last time
before going to do something else and I found the solution well the
problem and the solution.
the program now looks like this one
Thank you for your help it was really usefull

I suspect you’re var is getting incremented past the size of the array

You should add some puts statements around lines 14-15
and see how the value of var changes, and how it compares to the length
of unsorted.

cheers

On Fri, Feb 3, 2012 at 2:58 AM, andres d. [email protected]
wrote:

The program is done !!! i was only checking it for the last time
before going to do something else and I found the solution well the
problem and the solution.
the program now looks like this one
Thank you for your help it was really usefull

Attachments:
http://www.ruby-forum.com/attachment/6949/sort_cor.rb

Hi Andes,

I took the liberty to propose an alternative to the
first block of your program. I am afraid some
aspects of your program are not really Ruby idiomatic.

This is meant as “constructive criticism”, I hope you
can appreciate it. If not, sorry upfront.

def get_words [].tap do |a| while !(input = gets.chomp).empty? a << input end end end

puts “Hello, enter all the words you want, finish with empty line”
words = get_words
puts “The words you entered are:”
puts words

Some highlights:

  • put that functionality to read the words in a separate function
    and test it separately. Then you can also reuse it more easily.

  • Use [].tap{|a| a<< stuff} so you do not have to return the
    result array explicitly (I am not having a variable “words”
    or “array” in the function, it is returned as the final result but
    not stored in an explicit local variable; so I can impossibly
    forget to return the built up array at the end, because “tap”
    returns it automatically

  • don’t do “while true … break … end”
    use “while (data is valid) … do something with the data … end”
    the “break” in your version burns in my eyes.

  • take note of the special ‘while !(input = gets.chomp)’ construct
    with a single ‘=’ (not a double ‘==’) in the condition for while.
    Some people may find it not optimal to make an assignment,
    but it is the style I prefer for that use case. I am open to
    alternatives
    for that …

  • don’t store the data that is not valid (the empty string) in the array
    and then delete it afterwards. Evaluate the validity of the data
    before storing it in the array.

  • a more advanced aspect is that inside the block of “tap”, there
    is no variable used that comes from the outside of the block.
    That makes for safer code as there is less chance for accidental
    dependency of a variable that is set higher-up in the code.
    This is also the main reason for short functions, less chance for
    unintended dependencies on far-away variables.

Sorry for being critical, but I honestly hope you can take the time
to analyze my comments and learn some neat “Ruby” tricks from it.

Success with Ruby and welcome :slight_smile:

Peter

On Fri, Feb 3, 2012 at 12:25 PM, Peter V.
[email protected]wrote:

Hi Andes,

I see now that I misread your name (it should be Andres if I see
correctly).

Sorry for that,

Peter

2012/2/3 Peter V. [email protected]:

def get_words [].tap do |a| while !(input = gets.chomp).empty? a << input end end end

Aw. Do not abuse #tap, please. It’s extremely unreadable, especially
to a beginner.

  • Use [].tap{|a| a<< stuff} so you do not have to return the
    result array explicitly (I am not having a variable “words”
    or “array” in the function, it is returned as the final result but
    not stored in an explicit local variable; so I can impossibly
    forget to return the built up array at the end, because “tap”
    returns it automatically

There is no advantage to using constructs with tap over regular
variable I know of. IMO #tap should only be used to “inject” debugging
or other side-effects into a long method chain. (Although, if you have
a method chain so long, you probably have other problems…)

– Matma R.

On Fri, Feb 3, 2012 at 6:46 PM, Bartosz Dziewoński
[email protected]wrote:

Aw. Do not abuse #tap, please. It’s extremely unreadable, especially
to a beginner.

Thanks for the feedback.

I find it quite readable, because it take the recipient (an empty array here), "augments" it, and then just returns it back. At least for me, I love it, because otherwise there is always a chance I forget the (return) as last line of the function.

But, my argument is subjective …

a method chain so long, you probably have other problems…)

Could you kindly provide a clearer alternative for this functionality
then?

Interested,

Peter

Personally I have no problems using:

def get_words
ret = []
while !(input = gets.chomp).empty?
ret << input
end
return ret
end

I think that what I also dislike about using #tap in this scenario is
that you have to scan the entire function to see what it returns. In
my example, it clearly returns a variable named ret, and you can
easily look for this name in the code, see it defined and filled. In
your, it returns a value of the block inside, which might return
anything = so you scroll to the top, only then see it’s a #tap, then
looks for the variable name it uses inside the block, and only now you
see what is this array filled with.

Obviously which one you prefer is subjective; just my two cents. But
I’m pretty sure that the “declare accumulator, fill it, return it” is
easily recognizable for anyone - complete beginner and a convert from
any other language - while #tap is Ruby-specific and a cryptic for
newbies.

(I don’t know Python well, but what the yield keyword does in it in an
interesting way to solve this problem.)

– Matma R.

2012/2/3 Peter V. [email protected]:

Thank you for the clarification :slight_smile:

Agree to disagree?

Peter

Haha, yeah, I guess :slight_smile:

– Matma R.

On Fri, Feb 3, 2012 at 7:16 PM, Bartosz Dziewoński
[email protected]wrote:

I think that what I also dislike about using #tap in this scenario is
easily recognizable for anyone - complete beginner and a convert from
any other language - while #tap is Ruby-specific and a cryptic for
newbies.

Thank you for the clarification :slight_smile:

Agree to disagree?

Peter