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42 lines
1.1 KiB
Markdown
42 lines
1.1 KiB
Markdown
# Spread assignment
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In a spread assignment, a variable can be prefixed with `...` in front of the variable, all the remaining elements can be expanded into the variable. This is called a spread assignment.
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```erg
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[x, ... .y] = [1, 2, 3]
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assert x == 1
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assert y == [2, 3].
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x, ... .y = (1, 2, 3)
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assert x == 1
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assert y == (2, 3)
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```
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## Extract assignment
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If nothing is written after `...`, the remaining elements are ignored and an assignment is made. This type of expansion assignment is specifically called an extract assignment.
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Extract assignment is a useful syntax for bringing certain attributes local to a module or record.
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```erg
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{sin; cos; tan; ...} = import "math"
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```
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This way, `sin`, `cos`, `tan` can be used locally from then on.
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You can do the same with records.
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```erg
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record = {x = 1; y = 2}
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{x; y; ...} = record
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```
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If you want to expand all of them, use `{*} = record`, this is equivalent to `open` in OCaml and so on.
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```erg
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record = {x = 1; y = 2}
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{*} = record
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assert x == 1 and y == 2
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```
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<p align='center'>
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<a href='./27_comprehension.md'>Previous</a> | <a href='./29_decorator.md'>Next</a>
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</p>
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