Operators Reference

1st chunk of `doc/manual/source/language/operators.md`

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# Operators

| Name                                   | Syntax                                     | Associativity | Precedence |
|----------------------------------------|--------------------------------------------|---------------|------------|
| [Attribute selection]                  | *attrset* `.` *attrpath* \[ `or` *expr* \] | none          | 1          |
| [Function application]                 | *func* *expr*                              | left          | 2          |
| [Arithmetic negation][arithmetic]      | `-` *number*                               | none          | 3          |
| [Has attribute]                        | *attrset* `?` *attrpath*                   | none          | 4          |
| List concatenation                     | *list* `++` *list*                         | right         | 5          |
| [Multiplication][arithmetic]           | *number* `*` *number*                      | left          | 6          |
| [Division][arithmetic]                 | *number* `/` *number*                      | left          | 6          |
| [Subtraction][arithmetic]              | *number* `-` *number*                      | left          | 7          |
| [Addition][arithmetic]                 | *number* `+` *number*                      | left          | 7          |
| [String concatenation]                 | *string* `+` *string*                      | left          | 7          |
| [Path concatenation]                   | *path* `+` *path*                          | left          | 7          |
| [Path and string concatenation]        | *path* `+` *string*                        | left          | 7          |
| [String and path concatenation]        | *string* `+` *path*                        | left          | 7          |
| Logical negation (`NOT`)               | `!` *bool*                                 | none          | 8          |
| [Update]                               | *attrset* `//` *attrset*                   | right         | 9          |
| [Less than][Comparison]                | *expr* `<` *expr*                          | none          | 10         |
| [Less than or equal to][Comparison]    | *expr* `<=` *expr*                         | none          | 10         |
| [Greater than][Comparison]             | *expr* `>` *expr*                          | none          | 10         |
| [Greater than or equal to][Comparison] | *expr* `>=` *expr*                         | none          | 10         |
| [Equality]                             | *expr* `==` *expr*                         | none          | 11         |
| Inequality                             | *expr* `!=` *expr*                         | none          | 11         |
| Logical conjunction (`AND`)            | *bool* `&&` *bool*                         | left          | 12         |
| Logical disjunction (`OR`)             | *bool* <code>\|\|</code> *bool*            | left          | 13         |
| [Logical implication]                  | *bool* `->` *bool*                         | right         | 14         |
| [Pipe operator] (experimental)         | *expr* `\|>` *func*                        | left          | 15         |
| [Pipe operator] (experimental)         | *func* `<\|` *expr*                        | right         | 15         |


<!-- TODO(@rhendric, #10970): ^ rationalize number -> int/float -->

## Attribute selection

> **Syntax**
>
> *attrset* `.` *attrpath* \[ `or` *expr* \]

Select the attribute denoted by attribute path *attrpath* from [attribute set] *attrset*.
If the attribute doesn’t exist, return the *expr* after `or` if provided, otherwise abort evaluation.


## Function application

> **Syntax**
>
> *func* *expr*

Apply the callable value *func* to the argument *expr*. Note the absence of any visible operator symbol.
A callable value is either:
- a [user-defined function][function]
- a [built-in][builtins] function
- an attribute set with a [`__functor` attribute](./syntax.md#attr-__functor)

Title: Operators Reference

Summary

This document provides a comprehensive table of operators, detailing their names, syntax, associativity, and precedence within the language. It covers a wide range of operators including attribute selection, function application, various arithmetic operations (negation, multiplication, division, subtraction, addition), list and string concatenations, logical operations (NOT, AND, OR, implication), comparison operators (less than, greater than, equality), and an update operator. Following the table, the document offers detailed explanations for 'Attribute selection' and 'Function application'. Attribute selection allows retrieving an attribute from a set, with an optional fallback expression, while function application describes how callable values (user-defined functions, built-ins, or `__functor` attribute sets) are applied to arguments without an explicit operator symbol.