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Create an array of letters starting after A and ending after Z, i.e. (from B to AC)

I am working with Roo Gem and wanted to extract data from a spreadsheet based on standard A1 syntax.

I have columns in a spreadsheet outside of Z, so Excel does all the column positions AA, AB, AC.

I want to create an array for W columns in AH.

Ruby doesn't seem to like it when the top range goes past Z, but didn't start with A ??

Any ideas how to ("B".."AC").to_a

not get[]

Here is the main problem with irb.

("A".."Z").to_a
#=> ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]
("B".."Z").to_a
#=> ["B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]
("A".."AC").to_a
#=> ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "AA", "AB", "AC"]
("B".."AC").to_a
#=> []
+3


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4 answers


how about this?

("A".."AC").to_a.drop(1)

you can remove any amount elements

you like and it just includes 1 array and 1 array.

An integer can be replaced with someting, which returns the position of a letter in the alphabet.



class Array
  def from(column)
    drop(find_index(column).to_i)
  end
end

("A".."AC").to_a.from('F')
#=> ["F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "AA", "AB", "AC"]

Using the class Range

directly, thanks to @ sagarpandya82

class Range
  def from(column)
    to_a.drop(find_index(column).to_i)
  end
end

("A".."AC").from('F')
#=> ["F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "AA", "AB", "AC"]
+3


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Use Kernel#loop

to create an empty array. The loop is interrupted when the current value is equal to the second parameter. To return the newly constructed array o

, we pass o

as an argument to break

, which by default returns nil

.



def cols a, b
  loop.with_object([]) do |_, o|
    o << a
    break(o) if a == b
    a = a.next
  end
end  

cols('W','AH')
 #=> ["W", "X", "Y", "Z", "AA", "AB", "AC", "AD", "AE", "AF", "AG", "AH"]

cols("A","Z")
 #=> ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
 #    "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]

cols("B","Z")
 #=>  ["B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N",
 #     "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]

cols("A","AC")
 #=> ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
 #    "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
 #    "AA", "AB", "AC"]

cols("B","AC")
 #=> ["B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N",
 #    "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "AA",
 #    "AB", "AC"]
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The mathematical answer would be:

A => AH = (A => W) + (W => AH)

so W => AH = (A => AH) - (A => W)

Programmatic answer:

("A".."AH").to_a - ("A"..."W").to_a
#=> ["W", "X", "Y", "Z", "AA", "AB", "AC", "AD", "AE", "AF", "AG", "AH"]

...

in the second range makes it exceptional, i.e. without the "W".

More general answer:

r = "W".."AH"

("A"..r.end).to_a - ("A"...r.begin).to_a
#=> ["W", "X", "Y", "Z", "AA", "AB", "AC", "AD", "AE", "AF", "AG", "AH"]
+2


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Ruby String#succ

increases letters the way Excel increases column names:

'Z'.succ #=> "AA"

So, if you know the destination value is available through succ

, a simple loop works:

ary = ['W']
ary << ary.last.succ until ary.last == 'AH'

ary #=> ["W", "X", "Y", "Z", "AA", "AB", "AC", "AD", "AE", "AF", "AG", "AH"]

But with wrong values, it can easily become an endless loop.

For a more robust solution, you can write your own class:

class Column
  attr_reader :name

  def initialize(name)
    raise ArgumentError if name =~ /[^A-Z]/
    @name = name
  end

  def <=>(other)
    [name.length, name] <=> [other.name.length, other.name]
  end

  def succ
    Column.new(name.succ)
  end
end

It basically just wraps the column name, but it also respects the name length

:

[name.length, name] <=> [other.name.length, other.name]

This means that longer names appear after shorter ones. Names with the same length are compared lexicographically.

This allows you to generate the sequences you want:

r = Column.new('W')..Column.new('AH')
r.map(&:name)
#=> ["W", "X", "Y", "Z", "AA", "AB", "AC", "AD", "AE", "AF", "AG", "AH"]
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