array_split


`array_split`
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`array_split`

array_split — partitions a list or array into multiple lists or arrays.

Synopsis

array_split (list_or_array, nparts);

Arguments

list_or_array: Any list or array to be partitioned into multiple lists or arrays.
nparts: A number indicating the number of resulting arrays, or a function returning an index indicating which result part should contain each input element.

Returns

The input list_or_array, broken into parts. If the input is a list, the result will be a list of lists. If the input is an array, the result will be an array of arrays.

Description

This function partitions a collection into either a specified number of sub-collections, or into a set of sub-collections based on an indexing function. If the number of parts is specified as a number, the result will be a collection of at most that many sub-collections.

If the number of parts is specified as a function, then it must be a function taking two arguments and returning an integer. The return integer indicates the index of the sub-collection to which the input element is assigned. The indexing function has the form:

function (index, element)

Returning a partition index, where:

index: The index of this element within the input list_or_array, starting from zero.
element: The element of the input list_or_array corresponding to this index.

Examples

Gamma> players = [ "Matthews", "Marner", "Tavares", "Nylander", 
"Barrie", "Hyman", "Kapanen", "Kerfoot", "Rielly", "Spezza", 
"Mikheyev", "Muzzin", "Johnsson", "Holl" ];
[ "Matthews", "Marner", "Tavares", "Nylander", "Barrie", 
"Hyman", "Kapanen", "Kerfoot", "Rielly", "Spezza", 
"Mikheyev", "Muzzin", "Johnsson", "Holl" ]					
Gamma> n = 3;
3

// Split the array into N subarrays, filling from first to last
Gamma> array_split(players, n)
[[Matthews Marner Tavares Nylander Barrie] 
 [Hyman Kapanen Kerfoot Rielly Spezza] 
 [Mikheyev Muzzin Johnsson Holl]]


// Split the array into subarrays by the first letter of each element
Gamma> array_split(players, function(i,x) 
  { local c = tolower(x[0]) - 'a'; c < 0 ? 26 :  (c > 25 ? 26 : c); })
[nil [Barrie] nil nil nil nil nil [Hyman Holl] nil [Johnsson] 
     [Kapanen Kerfoot] nil [Matthews Marner Mikheyev Muzzin] 
     [Nylander] nil nil nil [Rielly] [Spezza] [Tavares]]


// Split the array into approximately equal subarrays 
// in a round-robin fashion 
Gamma> array_split(players, function(i,x) { i%n; })
[[Matthews Nylander Kapanen Spezza Johnsson] 
 [Marner Barrie Kerfoot Mikheyev Holl] 
 [Tavares Hyman Rielly Muzzin]]

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