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Describe the or operation on attribute sets slightly more

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Ana Hobden 2023-05-12 11:03:09 -07:00
parent 916da456cb
commit 17fb346ec6
2 changed files with 7 additions and 3 deletions
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2
doc/manual/src/language/operators.md
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@ -36,7 +36,7 @@
## Attribute selection
Select the attribute denoted by attribute path *attrpath* from [attribute set] *attrset*.
If the attribute doesn’t exist, return *value* if provided, otherwise abort evaluation.
If the attribute doesn’t exist, return the *expr* after `or` if provided, otherwise abort evaluation.
<!-- FIXME: the following should to into its own language syntax section, but that needs more work to fit in well -->

8
doc/manual/src/language/values.md
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@ -190,13 +190,17 @@ instance,
```
evaluates to `"Foo"`. It is possible to provide a default value in an
attribute selection using the `or` keyword. For example,
attribute selection using the `or` keyword:
```nix
{ a = "Foo"; b = "Bar"; }.c or "Xyzzy"
```
will evaluate to `"Xyzzy"` because there is no `c` attribute in the set.
```nix
{ a = "Foo"; b = "Bar"; }.c.d.e.f.g or "Xyzzy"
```
will both evaluate to `"Xyzzy"` because there is no `c` attribute in the set.
You can use arbitrary double-quoted strings as attribute names: