Map (higher-order function): Difference between revisions

Revision as of 08:42, 10 June 2024

Revision as of 07:51, 22 October 2024

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The concept of a map is not limited to lists: it works for sequential [[Container (abstract data type)|containers]], tree-like containers, or even abstract containers such as [[futures and promises]].

== Examples: mapping a list ==

Suppose wethere have ais list of integers <code>[1, 2, 3, 4, 5]</code> and would like to calculate the [[Square (algebra)|square]] of each integer. To do this, we first define a function to <code>square</code> a single number (shown here in [[Haskell (programming language)|Haskell]]):

<syntaxhighlight lang="haskell">

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</syntaxhighlight>

Afterwards we may, call:

<syntaxhighlight lang="haskell">

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=== Visual example ===

Below, youthere can see ais view of each step of the mapping process for a list of integers <code>X = [0, 5, 8, 3, 2, 1]</code> that we want to mapmapping into a new list <code>X'</code> according to the function <math>f(x) = x + 1</math> :

[[File:Mapping-steps-loillibe-new.gif|alt=applying map function processing steps|none|thumb|480x480px|View of processing steps when applying map function on a list]]

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</syntaxhighlight>

== Generalization ==

{{see also|Functor|Category theory}}