CODEWITHSUNDEEP
rubyloops
Jesse Jashinsky
Jesse Jashinsky

Reputation: 10663

Deleting While Iterating in Ruby?

I'm iterating over a very large set of strings, which iterates over a smaller set of strings. Due to the size, this method takes a while to do, so to speed it up, I'm trying to delete the strings from the smaller set that no longer needs to be used as it goes along. Below is my current code:

    Ms::Fasta.foreach(@database) do |entry|
        all.each do |set|
            if entry.header[1..40].include? set[1] + "|"
                startVal = entry.sequence.scan_i(set[0])[0]

                if startVal != nil
                    @locations << [set[0], set[1], startVal, startVal + set[1].length]
                    all.delete(set)
                end
            end
        end
    end

The problem I face is that the easy way, array.delete(string), effectively adds a break statement to the inner loop, which messes up the results. The only way I know how to fix this is to do this:

Ms::Fasta.foreach(@database) do |entry|
        i = 0

        while i < all.length
            set = all[i]

            if entry.header[1..40].include? set[1] + "|"
                startVal = entry.sequence.scan_i(set[0])[0]

                if startVal != nil
                    @locations << [set[0], set[1], startVal, startVal + set[1].length]
                    all.delete_at(i)
                    i -= 1
                end
            end

            i += 1
        end
    end

This feels kind of sloppy to me. Is there a better way to do this?

Upvotes: 16

Views: 15478

Answers (2)

Abhishek
Abhishek

Reputation: 1618

use 'arr.shift'

a=[1,2,3,4]
while(a.length!=0)
  print a
  a.shift
  print "\n"
end

Output:

[1, 2, 3, 4]
[2, 3, 4]
[3, 4]
[4]

Upvotes: -1

horseyguy
horseyguy

Reputation: 29895

use delete_if

array.delete_if do |v|
    if v.should_be_deleted?
        true
    else
        v.update
        false
    end
end

Upvotes: 38

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