Erlang list comprehension, traversing two lists and excluding values

Posted by ErJab on Stack Overflow See other posts from Stack Overflow or by ErJab
Published on 2010-03-13T04:35:19Z Indexed on 2010/03/13 4:37 UTC
Read the original article Hit count: 441

Filed under:

erlang

|

list-comprehension

I need to generate a set of coordinates in Erlang. Given one coordinate, say (x,y) I need to generate (x-1, y-1), (x-1, y), (x-1, y+1), (x, y-1), (x, y+1), (x+1, y-1), (x+1, y), (x+1, y+1). Basically all surrounding coordinates EXCEPT the middle coordinate (x,y). To generate all the nine coordinates, I do this currently:

[{X,Y} || X<-lists:seq(X-1,X+1), Y<-lists:seq(Y-1,Y+1)]

But this generates all the values, including (X,Y). How do I exclude (X,Y) from the list using filters in the list comprehension?

© Stack Overflow or respective owner

Related posts about erlang

Starting an Erlang slave node in escript fails when using custom Erlang in Ubuntu 10.4

as seen on Stack Overflow - Search for 'Stack Overflow'
I have the following escript: #!/usr/bin/env escript %%! -name [email protected] main(_) -> NodeName = test, Host = '127.0.0.1', Args = "", {ok, _Node} = slave:start_link(Host, NodeName, Args), io:format("Node started successfully!"). When running it on Ubuntu 10.04… >>> More
How to setup Erlang + Emacs with erlang.el?

as seen on Stack Overflow - Search for 'Stack Overflow'
I have downloaded and installed Erlang and EmacsW32. But how do I use erlang.el in Emacs? Where do I place it or install it? I have read Erlang/OTP R13B04 documentation and Erlang mode for Emacs documentation but I haven't found any information about how to set up it. >>> More
How do I install LFE on Ubuntu Karmic?

as seen on Stack Overflow - Search for 'Stack Overflow'
Erlang was already installed: $dpkg -l|grep erlang ii erlang 1:13.b.3-dfsg-2ubuntu2 Concurrent, real-time, distributed function ii erlang-appmon 1:13.b.3-dfsg-2ubuntu2 Erlang/OTP application monitor ii erlang-asn1 … >>> More
How to switch between the upper and lower pane in emacs?

as seen on Super User - Search for 'Super User'
I am using the erlang mode in Aquamacs. The mode, by default, creates a new pane and buffer "*erlang*" when I hit C-C C-K to compile an erlang file. (as seen in the attached screen shot) What is the easiest way to switch between these two panes? I do not think "C-x b" is applicable in this case… >>> More
Erlang: Mnesia or Mysql ?

as seen on Stack Overflow - Search for 'Stack Overflow'
What DMBS do you use with Erlang ? and Why ? >>> More

Related posts about list-comprehension

Advanced Python list comprehension

as seen on Stack Overflow - Search for 'Stack Overflow'
Given two lists: chars = ['ab', 'bc', 'ca'] words = ['abc', 'bca', 'dac', 'dbc', 'cba'] how can you use list comprehensions to generate a filtered list of words by the following condition: given that each word is of length n and chars is of length n as well, the filtered list should include only… >>> More
Python 3: unpack inner lists in list comprehension

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm running the following code on a list of strings to return a list of its words: words = [re.split('\\s+', line) for line in lines] However, I end up getting something like: [['import', 're', ''], ['', ''], ['def', 'word_count(filename):', ''], ...] As opposed to the desired: ['import', 're'… >>> More
Erlang list comprehension, traversing two lists and excluding values

as seen on Stack Overflow - Search for 'Stack Overflow'
I need to generate a set of coordinates in Erlang. Given one coordinate, say (x,y) I need to generate (x-1, y-1), (x-1, y), (x-1, y+1), (x, y-1), (x, y+1), (x+1, y-1), (x+1, y), (x+1, y+1). Basically all surrounding coordinates EXCEPT the middle coordinate (x,y). To generate all the nine coordinates… >>> More
[Python] How to use re match objects in a list comprehension

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a function to pick out lumps from a list of strings and return them as another list: def filterPick(lines,regex): result = [] for l in lines: match = re.search(regex,l) if match: result += [match.group(1)] return result Is there a way to reformulate… >>> More
How do I make this simple list comprehension?

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm new to python, and I'm trying to get to know the list comprehensions better. I'm not even really sure if list comprehension is the word I'm looking for, since I'm not generating a list. But I am doing something similar. This is what I am trying to do: I have a list of numbers, the length of… >>> More