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    <p>It's generally called <em>destructuring bind</em> in functional languages (which don't <em>have</em> assignments) and <em>destructuring assignment</em> in imperative languages.</p> <p>Some languages provide subsets of that feature and then call it something different. For example, in Python it works with Tuples, Lists or Sequences and is called <em>Tuple unpacking</em>, <em>List unpacking</em> or <em>Sequence unpacking</em>, in Ruby, it works with Arrays (or objects that are convertible to an array) and is called <em>parallel assignment</em>.</p> <p>Destructuring bind can get arbitrarily complex. E.g. this (imaginary) bind</p> <pre><code>[Integer(a), b, 2, c] = some_array </code></pre> <p>would assign the first element of <code>some_array</code> to <code>a</code>, the second element to <code>b</code> and the fourth element to <code>c</code>, but <em>only</em> if the first element is an <code>Integer</code>, the third element is equal to <code>2</code> and the length is 4. So, this even incorporates some conditional logic.</p> <p>Destructuring bind is a subset of more general <em>pattern matching</em>, which is a standard feature of functional languages like Haskell, ML, OCaml, F#, Erlang and Scala. The difference is that destructuring bind only lets you take apart a structure and bind its components to variables, whereas pattern matching also matches on values inside those structures and lets you make decisions and in particular lets you run arbitrary code in the context of the bindings. (You can see the above imaginary bind as half-way in between destructuring bind and pattern matching.)</p> <p>Here's the classical example of a <code>reverse</code> function in an imaginary language, written using pattern matching:</p> <pre><code>def reverse(l: List): List { match l { when [] { return [] } when [first :: rest] { return (reverse(rest) :: first) } } } </code></pre>
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    1. POWhat is the name of a [foo, bar] = ["foo", "bar"] feature?
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    1. USJörg W Mittag
    1. USJörg W Mittag
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    1. POWhat is the name of a [foo, bar] = ["foo", "bar"] feature?
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    1. COActually, in Python, it works for any sequence.
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      1. USMatthew Flaschen
    2. CO@Matthew Flaschen: Thanks. I added *Sequence Unpacking* and dropped the word "only" from the description.
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      1. USJörg W Mittag
    3. COI should have been more clear in both my answer (updated) and comment. Tuples and lists are particular kinds of sequence in Python, so tuple unpacking and list unpacking are just special cases of sequence unpacking.
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      1. USMatthew Flaschen
 

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