Home Accessibility Courses Twitter The Mouth Facebook Resources Site Map About Us Contact
Process every member of an array, and sort an array - Ruby

If you're wanting to process every member of an array, you've a choice ... you can write a loop to step through the key of each member, you can write a loop to step through each member itself, or you can call a method which operates on the array as a whole (i.e. the loop is hidden within a method. As I've been teaching a Ruby course this week, I'll give you examples in Ruby.

• Using a loop through the indexes:

  for posn in 0...places.length
    puts "Have a break in #{places[posn]}"

• Using a loop through the values:

  for place in places
    puts "Go to #{place} for a few days"

• Using a builtin iterator / enumerator method:

  puts places.collect {|place| "Sand and sea in #{place}"}

What are the advantages and disadvantages?

Looping through the indexes is always available (in any language). The syntax is longer / it's more complex to write, but it's very flexible. If you need to make use of the key within the loop (and not just the value), this will be the one that you want. And for an ordered list if you want to look back to the previous item, or forward to the next one, then you'll want to use this.

It's shorter and neater code to loop through the values if you don't care about the position number within the array

And it's going to be faster to use a built-in iterator or enumerator such as collect or map. The loop is still there, but it's hidden within the language implementation itself so it should run much faster as well as being even shorter code.

Complete sample program - and sample output too - [here].

The same source code example shows array sorting in Ruby - both in a default form:


and with a sort block specified, where you tell Ruby how to decide which of two elements comes first by passing it a comparator block:

  places.sort! {|left,right| left.length <=> right.length}

In both of these examples, I've used sort! rather than sort in order to alter the incoming array in situ - I didn't want a new, fresh copy as the original order was something I had no further use for. In the first half of the example, I could have used collect! rather than collect in order to modify the example in place, rather than create a fresh array.
(written 2011-04-21)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
R107 - Collections (Arrays and Hashes) in Ruby
  [4502] Reading and parsing a JSON object in Ruby - (2015-06-01)
  [4499] Significant work - beyond helloworld in Ruby - (2015-05-27)
  [4368] Shuffling a list - Ruby and Python - (2014-12-28)
  [3757] Ruby - a teaching example showing many of the language features in short but useful program - (2012-06-09)
  [3435] Sorta sorting a hash, and what if an exception is NOT thrown - Ruby - (2011-09-12)
  [3257] All possible combinations from a list (Python) or array (Ruby) - (2011-04-23)
  [3253] Is this number between? Does this list include? - Ruby - (2011-04-18)
  [2976] Creating, extending, traversing and combining Ruby arrays - (2010-09-30)
  [2621] Ruby collections and strings - some new examples - (2010-02-03)
  [2618] What are Ruby Symbols? - (2010-02-02)
  [2606] Sorting arrays and hashes in Ruby - (2010-01-30)
  [2291] Collection objects (array and hash) in Ruby - (2009-07-16)
  [991] Adding a member to a Hash in Ruby - (2006-12-16)

Back to
Multiple inputs, multiple out, ruby functions
Previous and next
Horse's mouth home
Forward to
Displaying a directory or file system tree - Linux
Some other Articles
Our library in Melksham
Morning in Melksham
Displaying a directory or file system tree - Linux
Process every member of an array, and sort an array - Ruby
Multiple inputs, multiple out, ruby functions
C++ - unknown array size, unknown object type. Help!
C++ - objects that are based on other objects, saving coding and adding robustness
C++ - how we teach the language and the concepts behind the language
4728 posts, page by page
Link to page ... 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95 at 50 posts per page

This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

Link to Ezine home page (for reading).
Link to Blogging home page (to add comments).

You can Add a comment or ranking to this page

© WELL HOUSE CONSULTANTS LTD., 2017: 404 The Spa • Melksham, Wiltshire • United Kingdom • SN12 6QL
PH: 01144 1225 708225 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho

PAGE: http://www.wellho.net/mouth/3255_Pro ... -Ruby.html • PAGE BUILT: Sat May 27 16:49:10 2017 • BUILD SYSTEM: WomanWithCat