mvellandi

mvellandi

Exploring Graphs with Elixir: Out of scope variable won't print (105, 107)

Exploring Graphs with Elixir by @tonyhammond: P.105, 107 — Ch 3 > Visualizing Graphs > Rendering with Graphviz

In making the water molecule and after writing a graph file using a variable, we’re told in 2 examples to print out the variable to inspect it using IO.puts

iex>​​ ​​with​​ ​​{:ok,​​ ​​dot}​​ ​​=​​ ​​Graph.to_dot(g)​​ ​​do​
​...>​​ ​​write_graph(dot,​​ ​​"dot/h2o.dot"​​)​
​...>​​ ​​end​
#GraphCommons.Graph<type: native, file: "...", data: "strict graph {\n...">​
​ 	
​iex>​​ ​​IO.puts​​ ​​dot​
strict graph {
​ 	    "O"
​ 	    "H"
​ 	    "H"
​ 	    "H" -- "O" [weight=1]
​ 	    "H" -- "O" [weight=1]
}​ 	
:ok

Maybe it’s just me, but this produces a function dot/0 not found error.
The variable “dot” is probably no longer in scope after having performed the first operation.

To make it print, I moved the print command above write_graph/2 command like so:

iex>​​ ​​with​​ ​​{:ok,​​ ​​dot}​​ ​​=​​ ​​Graph.to_dot(g)​​ ​​do​
...> IO.puts dot
...>​​ ​​write_graph(dot,​​ ​​"dot/h2o.dot"​​)​
...>​​ ​​end​
​ 
(graph output...)	​
#GraphCommons.Graph<type: native, file: "...", data: "strict graph {\n...">​

Marked As Solved

tonyhammond

tonyhammond

Author of Exploring Graphs with Elixir

Thanks for the catch.

I fixed this by reading it back in from the file store, as so:

iex> IO.puts read_graph(“dot/default.dot”).data

In two places.

Should be in the next beta.

Where Next?

Popular Pragmatic Bookshelf topics Top

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
raul
Page 28: It implements io.ReaderAt on the store type. Sorry if it’s a dumb question but was the io.ReaderAt supposed to be io.ReadAt? ...
New
jeremyhuiskamp
Title: Web Development with Clojure, Third Edition, vB17.0 (p9) The create table guestbook syntax suggested doesn’t seem to be accepted ...
New
New
jgchristopher
“The ProductLive.Index template calls a helper function, live_component/3, that in turn calls on the modal component. ” Excerpt From: Br...
New
akraut
The markup used to display the uploaded image results in a Phoenix.LiveView.HTMLTokenizer.ParseError error. lib/pento_web/live/product_l...
New
Henrai
Hi, I’m working on the Chapter 8 of the book. After I add add the point_offset, I’m still able to see acne: In the image above, I re...
New
dtonhofer
@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
roadbike
From page 13: On Python 3.7, you can install the libraries with pip by running these commands inside a Python venv using Visual Studio ...
New
New

Other popular topics Top

Devtalk
Hello Devtalk World! Please let us know a little about who you are and where you’re from :nerd_face:
New
PragmaticBookshelf
Brace yourself for a fun challenge: build a photorealistic 3D renderer from scratch! In just a couple of weeks, build a ray tracer that r...
New
PragmaticBookshelf
Learn from the award-winning programming series that inspired the Elixir language, and go on a step-by-step journey through the most impo...
New
PragmaticBookshelf
Ruby, Io, Prolog, Scala, Erlang, Clojure, Haskell. With Seven Languages in Seven Weeks, by Bruce A. Tate, you’ll go beyond the syntax—and...
New
ohm
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
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
husaindevelop
Inside our android webview app, we are trying to paste the copied content from another app eg (notes) using navigator.clipboard.readtext ...
New
PragmaticBookshelf
Author Spotlight: VM Brasseur @vmbrasseur We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
New
First poster: AstonJ
Jan | Rethink the Computer. Jan turns your computer into an AI machine by running LLMs locally on your computer. It’s a privacy-focus, l...
New

Sub Categories: