bwanab
convert binary floating and doubles in IEEE-754 format.
Hi. I’m new to elixir, so this could be obvious. I’m reading and writing to a device that uses a binary line format. The format is fixed. It also has integer fields, but they are easy to interpret. Floats and doubles are a bit harder, so I’m wondering and hoping that this is a problem that’s already been solved.
Here’s an example of what I’m looking at:
SSSSSSSSSSSSIIIIIIIIFFFFDDDDDDDD
Where S..S is a string descriptor.
IIII is an integer that I unpack with ((i1 <<< 32) + (i2 <<< 16) + (i3 <<< 8) + i4)
The ones I’m struggling with are FFFF (32 bit float) and DDDDDDDD (double prec float).
I know I can look at the IEEE-754 spec and figure this out, but I’m thinking there might be a solution already. For example in python given the FFFF, I can use struct.unpack(FFFF) to get the floating point value.
Most Liked
hauleth
Just remember that binary pattern matching also supports integers, so instead of manual addition and shifts you can do:
<<describe::binary-size(12), i1::little-integer-32, i2::little-integer-32, f1::float-32, f2::float-64>> = input
That is why I love working with binary data in Erlang. It is just so enormously easy.
NobbZ
This should totally do it for you, unless you have to deal with NaN and infinties…
iex(1)> bin = <<1.22::float>>
<<63, 243, 133, 30, 184, 81, 235, 133>>
iex(2)> <<x :: float>> = bin
<<63, 243, 133, 30, 184, 81, 235, 133>>
iex(3)> x
1.22
iex(4)> bin = <<1.22::float-size(32)>>
<<63, 156, 40, 246>>
hauleth
It is in docs for <<>>/1.
Popular in Questions
Other popular topics
Latest on Elixir Forum
Sponsor Spotlight
Supporting innovation across the BEAM ecosystem.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #deployment
- #library
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #channels
- #elixirconf
- #exunit
- #discussion
- #code-sync
- #javascript
- #podcasts
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ecto-query
- #elixir-ls
- #phoenix_html
- #iex
- #blog-post
- #graphql
- #genstage
- #ai
- #websockets
- #supervisor
- #advent-of-code
- #elixirconf-us
- #distillery
- #processes
- #forms
- #api
- #metaprogramming
- #security
- #performance
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Catch errors, track performance, monitor hosts and more.
Real-time error tracking, performance insights, and observability for devs.
Practical resources that improve the lives of professional developers.
Develop your skills with books, videos, and courses.
Producing high quality Elixir screencasts since 2017.
Courses that'll move you from confusion to "Aha, now I get it!"