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rubyarraysbinarypack

How do I turn an array of bits in an bitstring where each bit represents one boolean in Ruby

The question is pretty self explanatory. I want to turn something like [true, true, false, true] into the following bitstring 1101.

I assume I need to use Array.pack, but I can't figure out exactly how to do this.

Solution

  • It really depends on how exactly you want to represent the boolean Array.

    For [true, true, false, true], should it be 0b1101 or 0b11010000? I assume it's the former, and you may get it like this:

    data = [true, true, false, true]
out = data
  .each_slice(8) # group the data into segments of 8 bits, i.e., a byte
  .map {|slice|
    slice
      .map{|i| if i then 1 else 0 end } # convert to 1/0
      .join.to_i(2)                     # get the byte representation
  }
  .pack('C*')
p out #=> "\r"

    PS. There may be further endian problem depending on your requirements.