Ruby Delete From Array On Criteria - ruby

Question

I'm just learning Ruby and have been tackling small code projects to accelerate the process.
What I'm trying to do here is read only the alphabetic words from a text file into an array, then delete the words from the array that are less than 5 characters long. Then where the stdout is at the bottom, I'm intending to use the array. My code currently works, but is very very slow since it has to read the entire file, then individually check each element and delete the appropriate ones. This seems like it's doing too much work.
goal = File.read('big.txt').split(/\s/).map do |word|
word.scan(/[[:alpha:]]+/).uniq
end
goal.each { |word|
if word.length < 5
goal.delete(word)
end
}
puts goal.sample
Is there a way to apply the criteria to my File.read block to keep it from mapping the short words to begin with? I'm open to anything that would help me speed this up.

Answer 1

You might want to change your regex instead to catch only words longer than 5 characters to begin with:
goal = File.read('C:\Users\bkuhar\Documents\php\big.txt').split(/\s/).flat_map do |word|
word.scan(/[[:alpha:]]{6,}/).uniq
end
Further optimization might be to maintain a Set instead of an Array, to avoid re-scanning for uniqueness:
goal = Set.new
File.read('C:\Users\bkuhar\Documents\php\big.txt').scan(/\b[[:alpha:]]{6,}\b/).each do |w|
goal << w
end

Answer 2

In this case, use the delete_if method
goal => your array
goal.delete_if{|w|w.length < 5}
This will return a new array with the words of length lower than 5 deleted.
Hope this helps.

Answer 3

I really don't understand what a lot of the stuff you are doing in the first loop is for.
You take every chunk of text separated by white space, and map it to a unique value in an array generated by chunking together groups of letter characters, and plug that into an array.
This is way too complicated for what you want. Try this:
goal = File.readlines('big.txt').select do |word|
word =~ /^[a-zA-Z]+$/ &&
word.length >= 5
end
This makes it easy to add new conditions, too. If the word can't contain 'q' or 'Q', for example:
goal = File.readlines('big.txt').select do |word|
word =~ /^[a-zA-Z]+$/ &&
word.length >= 5 &&
! word.upcase.include? 'Q'
end
This assumes that each word in your dictionary is on its own line. You could go back to splitting it on white space, but it makes me wonder if the file you are reading in is written, human-readable text; a.k.a, it has 'words' ending in periods or commas, like this sentence. In that case, splitting on whitespace will not work.
Another note - map is the wrong array function to use. It modifies the values in one array and creates another out of those values. You want to select certain values from an array, but not modify them. The Array#select method is what you want.
Also, feel free to modify the Regex back to using the :alpha: tag if you are expecting non-standard letter characters.
Edit: Second version
goal = /([a-z][a-z']{4,})/gi.match(File.readlines('big.txt').join(" "))[1..-1]
Explanation: Load a file, and join all the lines in the file together with a space. Capture all occurences of a group of letters, at least 5 long and possibly containing but not starting with a '. Put all those occurences into an array. the [1..-1] discards "full match" returned by the MatchData object, which would be all the words appended together.
This works well, and it's only one line for your whole task, but it'll match
sugar'
in
I'd like some 'sugar', if you know what I mean
Like above, if your word can't contain q or Q, you could change the regex to
/[a-pr-z][a-pr-z']{4,})[ .'",]/i
And an idea - do another select on goal, removing all those entries that end with a '. This overcomes the limitations of my Regex