How to convert a string or integer to binary in Ruby

Question

How do you create integers 0  9 and math operators   -     in to  binary strings  For example    0   0000   1   0001         9   1001   Is there a way to do this with Ruby 1 8 6 without using a library

User · Answer

You would naturally use Integer to s 2   String to i 2  or   b  in a real program  but  if you re interested in how the translation works  this method calculates the binary representation of a given integer using basic operators   def int to binary x    p   0   two p   0   output         while two p   2  lt   x do     two p   2    p     output  lt  lt    two p  amp  x    two p     1     0       p    1   end     Reverse output to match the endianness of  b   output reverse end   To check it works   1 upto 1000  do  n    built in  custom      b    n   int to binary n    if built in    custom     puts  I expected   built in  but got   custom        exit 1   end   puts custom end

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I asked a similar question  Based on  sawa s answer  the most succinct way to represent an integer in a string in binary format is to use the string formatter     b    245   gt   11110101    You can also choose how long the string representation to be  which might be useful if you want to compare fixed-width binary numbers   1 upto 10  each    n  puts   04b    n   0001 0010 0011 0100 0101 0110 0111 1000 1001 1010

User · Answer

In ruby Integer class  to s is defined to receive non required argument radix called base  pass 2 if you want to receive binary representation of a string  Here is a link for an official documentation of String to s   1 upto 10  each    n   puts n to s 2

User · Answer

If you are looking for a Ruby class method I used this  and I have also included the tests   class Binary   def self binary to decimal binary      binary array   binary to s chars map  amp  to i      total   0      binary array each with index do  n  i        total    2     binary array length-i-1    n     end     total    end end  class BinaryTest  lt  Test  Unit  TestCase   def test 1    test1   Binary binary to decimal 0001     assert equal 1  test1   end   def test 8     test8   Binary binary to decimal 1000      assert equal 8  test8  end   def test 15     test15   Binary binary to decimal 1111      assert equal 15  test15  end   def test 12341     test12341   Binary binary to decimal 11000000110101      assert equal 12341  test12341  end end

User · Answer

I am almost a decade late but if someone still come here and want to find the code without using inbuilt function like to S then I might be helpful  find the binary def find binary number    binary          until number    0      binary  lt  lt  number 2     number   number 2   end   puts binary reverse join end

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Picking up on bta s lookup table idea  you can create the lookup table with a block  Values get generated when they are first accessed and stored for later    gt  gt  lookup table   Hash new    h  i  h i    i to s 2      gt      gt  gt  lookup table 1    gt   1   gt  gt  lookup table 2    gt   10   gt  gt  lookup table 20    gt   10100   gt  gt  lookup table 200    gt   11001000   gt  gt  lookup table   gt   1  gt  1   200  gt  11001000   2  gt  10   20  gt  10100

User · Answer

If you re only working with the single digits 0-9  it s likely faster to build a lookup table so you don t have to call the conversion functions every time   lookup table   Hash new  0  9  each   x      lookup table x    x to s 2      lookup table x to s    x to s 2    lookup table 5    gt   101  lookup table  8     gt   1000    Indexing into this hash table using either the integer or string representation of a number will yield its binary representation as a string   If you require the binary strings to be a certain number of digits long  keep leading zeroes   then change x to s 2  to sprintf   04b   x  where 4 is the minimum number of digits to use

User · Answer

You have Integer to s base  and String to i base  available to you   Integer to s base  converts a decimal number to a string representing the number in the base specified   9 to s 2     gt   1001    while the reverse is obtained with String to i base     1001  to i 2     gt  9

[ruby] How to convert a string or integer to binary in Ruby?

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