joustava

joustava

Genetic Algorithms in Elixir: Code throws error (page 111)

Not sure if I’m doing something wrong here, but it seems that this piece of code will throw errors:

def fitness_function(chromosome) do
    target = 'ILoveGeneticAlgorithms'
    encrypted = 'LIjs`B`k`qlfDibjwlqmhv'
    cipher = fn word, key -> Enum.map(word, & rem(&1 ^^^ key, 32768)) end
    key =
      chromosome.genes
      |> Enum.map(&Integer.to_string/1)
      |> Enum.join("")
      |> String.to_integer(2)

      guess = List.to_string(cipher.(encrypted, key))
      String.jaro_distance(target, guess)
end

As

String.jaro_distance(target, guess)

Doesn’t expect ‘charlists’ but binaries

** (FunctionClauseError) no function clause matching in String.Unicode.graphemes/1

    The following arguments were given to String.Unicode.graphemes/1:

        # 1
        'ILoveGeneticAlgorithms'

    Attempted function clauses (showing 1 out of 1):

        def graphemes(binary) when is_binary(binary)

    (elixir 1.10.3) lib/elixir/unicode/unicode.ex:252: String.Unicode.graphemes/1
    (elixir 1.10.3) lib/string.ex:2488: String.jaro_distance/2
    (genetic 0.1.0) lib/genetic.ex:24: anonymous fn/2 in Genetic.evaluate/3
    (elixir 1.10.3) lib/enum.ex:1396: Enum."-map/2-lists^map/1-0-"/2
    (genetic 0.1.0) lib/genetic.ex:23: Genetic.evaluate/3
    (genetic 0.1.0) lib/genetic.ex:116: Genetic.evolve/6
    scripts/code_breaker.exs:39: (file)

I’m running this on:

⟩ elixir --version
Erlang/OTP 23 [erts-11.0.2] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe]

Elixir 1.10.3 (compiled with Erlang/OTP 23)

Not sure if something has changed recently regarding this issue.

Also, it seems the capture operator ‘&’ is in the wrong place in the book and should be moved before the call to ‘rem’ otherwise a

** (ArithmeticError) bad argument in arithmetic expression: rem(#Function<1.106933999/1 in CodeBreaker.fitness_function/1>, 32768)
    :erlang.rem(#Function<1.106933999/1 in CodeBreaker.fitness_function/1>, 32768)
    scripts/code_breaker.exs:16: anonymous fn/2 in CodeBreaker.fitness_function/1
    (genetic 0.1.0) lib/genetic.ex:24: anonymous fn/2 in Genetic.evaluate/3
    (elixir 1.10.3) lib/enum.ex:1396: Enum."-map/2-lists^map/1-0-"/2
    (genetic 0.1.0) lib/genetic.ex:23: Genetic.evaluate/3
    (genetic 0.1.0) lib/genetic.ex:116: Genetic.evolve/6
    scripts/code_breaker.exs:33: (file)

will occur.
I think on the next page in the iex example it is the correct way.

First Post!

adkelley

adkelley

Strings in Elixir are inserted between double quotes. Therefore change: target = 'ILoveGeneticAlgorithms' to: target = "ILoveGeneticAlgorithms"

Where Next?

Popular Pragmatic Bookshelf topics Top

jeffmcompsci
Title: Design and Build Great Web APIs - typo “https://company-atk.herokuapp.com/2258ie4t68jv” (page 19, third bullet in URL list) Typo:...
New
mikecargal
Title: Hands-On Rust (Chap 8 (Adding a Heads Up Display) It looks like ​.with_simple_console_no_bg​(SCREEN_WIDTH*2, SCREEN_HEIGHT*2...
New
jdufour
Hello! On page xix of the preface, it says there is a community forum "… for help if your’re stuck on one of the exercises in this book… ...
New
mikecargal
Title: Hands-on Rust: question about get_component (page 295) (feel free to respond. “You dug you’re own hole… good luck”) I have somet...
New
alanq
This isn’t directly about the book contents so maybe not the right forum…but in some of the code apps (e.g. turbo/06) it sends a TURBO_ST...
New
swlaschin
The book has the same “Problem space/Solution space” diagram on page 18 as is on page 17. The correct Problem/Solution space diagrams ar...
New
nicoatridge
Hi, I have just acquired Michael Fazio’s “Kotlin and Android Development” to learn about game programming for Android. I have a game in p...
New
digitalbias
Title: Build a Weather Station with Elixir and Nerves: Problem connecting to Postgres with Grafana on (page 64) If you follow the defau...
New
taguniversalmachine
It seems the second code snippet is missing the code to set the current_user: current_user: Accounts.get_user_by_session_token(session["...
New
redconfetti
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
New

Other popular topics Top

AstonJ
A thread that every forum needs! Simply post a link to a track on YouTube (or SoundCloud or Vimeo amongst others!) on a separate line an...
New
Exadra37
I am thinking in building or buy a desktop computer for programing, both professionally and on my free time, and my choice of OS is Linux...
New
AstonJ
There’s a whole world of custom keycaps out there that I didn’t know existed! Check out all of our Keycaps threads here: https://forum....
New
AstonJ
I ended up cancelling my Moonlander order as I think it’s just going to be a bit too bulky for me. I think the Planck and the Preonic (o...
New
dimitarvp
Small essay with thoughts on macOS vs. Linux: I know @Exadra37 is just waiting around the corner to scream at me “I TOLD YOU SO!!!” but I...
New
AstonJ
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first: asdf plugin-upd...
New
PragmaticBookshelf
Learn different ways of writing concurrent code in Elixir and increase your application's performance, without sacrificing scalability or...
New
AstonJ
We’ve talked about his book briefly here but it is quickly becoming obsolete - so he’s decided to create a series of 7 podcasts, the firs...
New
PragmaticBookshelf
Author Spotlight Jamis Buck @jamis This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
sir.laksmana_wenk
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc. However, I don’t...
New

Sub Categories: