inreoh
Genetic Algorithms in Elixir: wrong syntax in ch. 4, termination criteria for one_max ?
@seanmor5
In chapter 4 of p1.0 (page 89 of 262 in the epub version), the code for the avg termination criterion looks like this:
def terminate?(population) do
avg =
population
|> Enum.map(&(Enum.sum(&1) / length(&1)))
avg == 21
end
For me, this causes a syntax error:
protocol Enumerable not implemented for %Types.Chromosome
Presumably because the call to fitness_function() is missing. This version works for me:
avg =
population
|> Enum.map(&OneMax.fitness_function/1)
|> Enum.sum()
|> (fn x -> x / length(population) end).()
although it’s not very elegant (esp. the last line looks ugly), so I’d much prefer something closer to the original version.
Popular Pragmatic Bookshelf topics
Title: Web Development with Clojure, Third Edition, pg 116
Hi - I just started chapter 5 and I am stuck on page 116 while trying to star...
New
Hi Jamis,
I think there’s an issue with a test on chapter 6. I own the ebook, version P1.0 Feb. 2019.
This test doesn’t pass for me:
...
New
I can’t setup the Rails source code. This happens in a working directory containing multiple (postgres) Rails apps.
With:
ruby-3.0.0
s...
New
In case this helps anyone, I’ve had issues setting up the rails source code. Here were the solutions:
In Gemfile, change
gem 'rails'
t...
New
The test is as follows:
Scenario: Intersecting a scaled sphere with a ray
Given r ← ray(point(0, 0, -5), vector(0, 0, 1))
And s ← sphere...
New
I found an issue in Chapter 7 regarding android:backgroundTint vs app:backgroundTint.
How to replicate:
load chapter-7 from zipfile i...
New
On page 78 the following code appears:
<%= link_to ‘Destroy’, product,
class: ‘hover:underline’,
method: :delete,
data: { confirm...
New
@parrt
In the context of Chapter 4.3, the grammar Java.g4, meant to parse Java 6 compilation units, no longer passes ANTLR (currently 4....
New
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
New
I’ve got to the end of Ch. 11, and the app runs, with all tabs displaying what they should – at first. After switching around between St...
New
Other popular topics
Reading something? Working on something? Planning something? Changing jobs even!?
If you’re up for sharing, please let us know what you’...
New
No chair. I have a standing desk.
This post was split into a dedicated thread from our thread about chairs :slight_smile:
New
Design and develop sophisticated 2D games that are as much fun to make as they are to play. From particle effects and pathfinding to soci...
New
New
New
Build efficient applications that exploit the unique benefits of a pure functional language, learning from an engineer who uses Haskell t...
New
Author Spotlight
Jamis Buck
@jamis
This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
I am trying to crate a game for the Nintendo switch, I wanted to use Java as I am comfortable with that programming language. Can you use...
New
There appears to have been an update that has changed the terminology for what has previously been known as the Taskbar Overflow - this h...
New
Fight complexity and reclaim the original spirit of agility by learning to simplify how you develop software. The result: a more humane a...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /ruby
- /wasm
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /emacs
- /haskell
- /java
- /svelte
- /onivim
- /typescript
- /kotlin
- /c-plus-plus
- /crystal
- /tailwind
- /react
- /gleam
- /ocaml
- /flutter
- /elm
- /vscode
- /ash
- /opensuse
- /html
- /centos
- /php
- /deepseek
- /zig
- /scala
- /sublime-text
- /textmate
- /lisp
- /react-native
- /debian
- /nixos
- /agda
- /kubuntu
- /django
- /arch-linux
- /deno
- /revery
- /nodejs
- /ubuntu
- /manjaro
- /spring
- /diversity
- /lua
- /julia
- /markdown
- /c








