| [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)

> **Warning**
>
> [List][list] items are also separated by whitespace, which means that function calls in list items must be enclosed by parentheses.

## Has attribute

> **Syntax**
>
> *attrset* `?` *attrpath*

Test whether [attribute set] *attrset* contains the attribute denoted by *attrpath*.
The result is a [Boolean] value.

See also: [`builtins.hasAttr`](@docroot@/language/builtins.md#builtins-hasAttr)



After evaluating *attrset* and *attrpath*, the computational complexity is O(log(*n*)) for *n* attributes in the *attrset*

## Arithmetic

Numbers will retain their type unless mixed with other numeric types:
Pure integer operations will always return integers, whereas any operation involving at least one floating point number returns a floating point number.

Evaluation of the following numeric operations throws an evaluation error:
- Division by zero
- Integer overflow, that is, any operation yielding a result outside of the representable range of [Nix language integers](./syntax.md#number-literal)

See also [Comparison] and [Equality].

The `+` operator is overloaded to also work on strings and paths.


## String concatenation

> **Syntax**
>
> *string* `+` *string*

Concatenate two [strings][string] and merge their [string contexts](./string-context.md).


## Path concatenation

> **Syntax**
>
> *path* `+` *path*

Concatenate two [paths][path].
The result is a path.


## Path and string concatenation

> **Syntax**
>
> *path* + *string*