Array Demo

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What information is available about an Array?

The Array type has the following members:

Array Append(Array array)

Answer this array after the supplied array has been appended on the end.

Array Collect(Block block)

Evalute the given block once for each object in the array; answer a new array containing the result of each block evaluation.

Integer Count

Answer the number of objects in the array

Object IsEmpty

Answer true if this object is empty, else false

Object Item(Integer index)

Answer the item at the given index

Array Reverse

Answer a new array that is in reverse order of the original array

Array ReverseSort

Sort the array; answer a new array (that is sorted)

Array ReverseSortBy(Block block)

Sort the array; evaluate the block for each object in the array to determine the object used to order that item in the sort

Array Select(Block block)

Evaluate the block for each item in the array; answer a new Array that includes on those objects for which the block evaluated to true.

Array Snip(Integer maxCount)

Answer a new array that is a copy of this array, but trimmed to have no more than the given number of objects.

Array Sort

Sort the array; answer a new array (that is sorted)

Array SortBy(Block block)

Sort the array; evaluate the block for each object in the array to determine the object used to order that item in the sort

String ToOneString

Answer a single string that is the concatenation of all of the objects in the array converted to strings

Object ToPresentation

Convert this object to a Presentation

Array Unique

Answer the unique elements in this array

Examples

Append

 [1,2,3].Append([4,5,6]).Collect{each | ["        *", each, Newline]}

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Item

 [1,2,3].Item(0)

1

Sort

 [2,1,3].Sort

123

 ["a", "c", "d", "b", "b"].Sort

abbcd

Count

 [1,2,3].Count

3

ToOneString

 [1,2,3].ToOneString

123

Nested arrays

 [1,2,[4,3,2,1]].Item(2).Count

4

Collect

Apply the block parameter to each element in the array and return a new array. Collect is a method which is very functional programming-like in nature. Think of it working a bit like foreach in C# or VB.

Help

Can someone please explain how .Collect(each | ) is different than a foreach in C#? From what I can tell, you name object as the first parameter and after the pipe, you put the code you want. Wouldn't it be nice if the syntax of the commands was explained somewhere?

Answer

Foreach-like statements only do things with elements. Collect collects them into array of results. You can apply another Select or Collect on these results. Like in: [1,2,3,4,5].Collect{x | x*x}.Select{x | x>10}

 ["a","aa","aaa"].Collect{each | each.Length}

123

SortBy

Sort "one", "two", "three", "four", "five" according to the length of each string:

 ["one", "two", "three", "four", "five"].SortBy{each | each.Length}.Collect{each | [each, Newline]}.ToOneString

two

one

four

five

three

Notice that SortBy is not a StableSort.

• Q What is a StableSort?
• Q How do I sort an array descending instead of ascending?
• A For numbers and topics with numeric properties, subtract the value of the sort key from 0. For example: "[ 1, 3, 6 ].SortBy { x | 0.Subtract( x ) }" -- ScottAinsworth [2006-02-26]

Unique

 [1,2,3].Append([2,3,4,5,6]).Unique.Collect{each | ["        *", each, Newline]}

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Multiple Keyword OR Selection

 :SelectCategoryTopics:{ keyword |
   namespace.Topics.Select{ each |
     each.HasProperty("Category") }.Select{ each |
       each.GetProperty("Category").Contains(keyword) }.Collect{ each | each }
 }

TestJwd.ArrayDemo(3:1) : Expected right parenthesis ')' or comma ','; got TokenEndOfInput

With

ReflectionLibrary

Discussion

• Why was Collect named as it was. Why not ForEach? I'm trying my best to understand it and how it is best used. -- MikeSchinkel [7/5/2004]
• [1,2,3].ToOneString seems to be something that one would use frequently. How about some syntactic sugar? -- MikeSchinkel [7/5/2004]
• Does anyone ever read and/or answer these questions? -- MikeSchinkel [2004-07-19]
• No. And one of the AnnoyingThingsAboutWiki. -- TimSmith [2005-01-13]
• How can I do the equivalent of a "SELECT DISTINCT" in SQL? Maybe adding a Distinct() function similar in syntax to Collect() and Sort()? -- MikeSchinkel [2004-07-19]
• There is a Unique method that returns unique values -- RoystonShufflebotham [2005-07-07]
• Is there a way to parse a coma separated string, as a page propertie ? -- ArnoTournier [2004-09-30]
• You can use the GetListProperty() method of TopicInfoType to do just this. -- JimmySieben [2005-08-27]
• How to get a normal array out of a nested one (e.g. all list property values of all topics)? I need something like this:

   [ Page1Keyword1, Page2Keyword1, [ Page3Keyword1, Page3Keyword2 ], Page4Keyword1 ].UNION.Unique.Collect{each | [each, Newline]}.ToOneString
  

  -- MichaelStamenov [7/22/2005]

TestJwd.ArrayDemo(1:53) : No such property or function: Array.Union

Is MichaelStamenov right? -- JamesRoeSmith.

TestJwd.ArrayDemo(1:21) : No such property or function: Array.Union

• Why use ToOneString if ToString does the same, and I can use it generally (that is, I can use GetProperty(x.ToString) and pass both Array or String as x? -- HerbyVojčík [2006-04-27]