Comments on: Surveying Emacs Lisp

By: Charmain Panama

Charmain Panama — Thu, 04 Feb 2010 09:45:21 +0000

There is evidently a lot for me to study outside of my books. Thanks for the important read,

By: linkfeedr » Blog Archive » lisp - RSS Indexer (beta)

linkfeedr » Blog Archive » lisp - RSS Indexer (beta) — Tue, 14 Apr 2009 19:57:11 +0000

[...] This article was found on emacs life. Click here to visit the full article on the original website. Surveying Emacs Lisp – A good article that looks at Emacs Lisp and a little Ruby. … more on the original website [...]

By: Stephen Bach

Stephen Bach — Sat, 11 Apr 2009 17:13:52 +0000

Ryan, it’s a little counterintuitive, but even with your change the function doesn’t work exactly right. Try this input to see:

strings = "a b c d e f g".split
column_count = 3

By: Ryan Davis

Ryan Davis — Sat, 11 Apr 2009 09:23:06 +0000

I’d actually come up with this before reading the numerous comments. The only thing bitti needed was to calculate the number of rows and use that for each_slice.

require 'enumerator'
 
def new_columnize(strings, column_count)
  r = []
  rows = (strings.size / column_count.to_f).round
  strings.each_slice(rows) { |a| r << a }
  r
end

By: Stephen Bach

Stephen Bach — Fri, 03 Apr 2009 03:09:41 +0000

Fester, bitti, your versions of columnize actually ensure there will be column_count rows, not columns. Slightly different.

By: bitti

bitti — Thu, 02 Apr 2009 18:57:46 +0000

Sorry, forgot the pre tag:

def columnize(strings, column_count)
  cols = []
  strings.each_slice(column_count) { |row| cols << row }
  cols
end

By: bitti

bitti — Thu, 02 Apr 2009 18:54:32 +0000

For columnize use each_slice:

def columnize(strings, column_count)
cols = []
strings.each_slice(column_count) { |row| cols << row }
cols
end

By: Stephen Bach

Stephen Bach — Wed, 01 Apr 2009 17:41:20 +0000

A friend points out that because of Emacs Lisp’s dynamic scope, the lambda in my columnize function is of uncertain correctness; if the implementation of reduce happens to bind a variable named nrows, the sky will fall.

None of the proposed rewrites show that mistake, so good for you folks.

By: Fester

Fester — Wed, 01 Apr 2009 10:53:20 +0000

Maybe I am missing something from your version of columnize, but maybe you should consider this:

def columnize(strings, columns)
  cols = []
  strings.each_slice(columns){|x| cols << x}
  return cols
end

By: links for 2009-03-31 « My Weblog

links for 2009-03-31 « My Weblog — Wed, 01 Apr 2009 04:03:25 +0000

[...] Surveying Emacs Lisp – items.sjbach.com (tags: emacs) [...]