Lulu Arrays — Values and Counts

Introduction

If you have imported the lulu.Array class as

local Array = require 'lulu.Array'

Then, you have access to the following methods:

Array:counts()
Returns a map of the values in self to the number of times they occur.

Array:to_set()
Returns a set from self. The set is a table whose keys are the unique values in self. The associated values in that table are always true.

Array:to_map()
Returns a table where the keys are the values in self, and the table values are the corresponding indices.
If a value occurs more than once in an array, the table value will be the index of the first occurrence.

Example:

1local arr = Array{'a', 'b', 'a', 'c', 'b', 'a'}
putln("The array:       %t", arr)
putln("As a set:        %t", arr:to_set())
putln("As a map:        %t", arr:to_map())
putln("Value counts:    %t", arr:counts())

1: We set up an Array with some repeated values.

Output:

The array:       [ "a", "b", "a", "c", "b", "a" ]
1As a set:        { a = true, b = true, c = true }
2As a map:        { a = 1, b = 2, c = 4 }
3Value counts:    { a = 3, b = 2, c = 1 }

1: There are just three distinct elements in the array.
2: “a” occurs more than once, but the first occurrence is at index 1, and ditto for “b” at index 2
3: In all, “a” occurs 3 times, “b” occurs twice, and “c” occurs just once.

Introduction

See Also