How to convert 64 bit binary string to a double float in ruby?

Question

I am wondering how to convert a 64 bit binary string to a double float in ruby. The string that I have is as follows:

binaryString = "0011111111110000000000000000000000000000000000000000000000000000"

Using an online converter (http://www.binaryconvert.com/convert_double.html?) I know that the value should be 1.0. However, I'm attempting to use the ruby unpack to convert to double, and I'm not getting the correct result.

double_value = binaryString.unpack("G")

Gives me double_value = 1.3983819593719592e-76

I've tried other directives like "F" and "D", but none yield correct results.

Any ideas what I am doing wrong? Thank you for the help!

Presumably binaryString is a string, so you need quotation marks on the right. (As written, binaryString is an integer whose digits are all zeros and ones, and whose two leading zeroes are of no significance) If it is meant to be a string, why not use it's integer value, binaryString.to_i(2) # => 4607182418800017408? You need to edit the question to correct or clarify. — Cary Swoveland
– Cary Swoveland, Commented Jun 21, 2018 at 16:34
Thanks for the reply and suggestion. I added quotes to show that binaryString is, in fact, a string. I am not using the integer value because I know that binaryString correctly represents a double value of 1.0 per the online converter. I'm trying to get ruby to covert to the correct value. I want some way to have ruby yield 1.0 from the binaryString given. — Z. Nahman
– Z. Nahman, Commented Jun 21, 2018 at 16:43

Stefan · Accepted Answer · 2018-06-21 16:44:12Z

3

unpack expects binary data, so you have to pack your bit string first using B:

b = '0011111111110000000000000000000000000000000000000000000000000000'

[b].pack('B*').unpack1('G')
#=> 1.0

answered Jun 21, 2018 at 16:44

Stefan

115k14 gold badges157 silver badges233 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Z. Nahman Over a year ago

Works like a charm. Thank you for your help!

Collectives™ on Stack Overflow

How to convert 64 bit binary string to a double float in ruby?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related