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   [Null](@docroot@/language/types.md#type-null) value

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   `123`

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   An [integer](@docroot@/language/types.md#type-int)

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   `3.141`

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   A [floating point number](@docroot@/language/types.md#type-float)

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   `/etc`

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   An absolute [path](@docroot@/language/types.md#type-path)

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   `./foo.png`

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   A [path](@docroot@/language/types.md#type-path) relative to the file containing this Nix expression

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   `~/.config`

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   A home [path](@docroot@/language/types.md#type-path). Evaluates to the `"<user's home directory>/.config"`.

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   `<nixpkgs>`

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   A [lookup path](@docroot@/language/constructs/lookup-path.md) for Nix files. Value determined by [`$NIX_PATH` environment variable](../command-ref/env-common.md#env-NIX_PATH).

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   *Compound values*

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   `{ x = 1; y = 2; }`

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   An [attribute set](@docroot@/language/types.md#attribute-set) with attributes named `x` and `y`

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   `{ foo.bar = 1; }`

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   A nested set, equivalent to `{ foo = { bar = 1; }; }`

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   `rec { x = "foo"; y = x + "bar"; }`

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   A [recursive set](@docroot@/language/syntax.md#recursive-sets), equivalent to `{ x = "foo"; y = "foobar"; }`.

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   `[ "foo" "bar" "baz" ]`

   `[ 1 2 3 ]`

   `[ (f 1) { a = 1; b = 2; } [ "c" ] ]`

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   [Lists](@docroot@/language/types.md#list) with three elements.

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   *Operators*

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   `"foo" + "bar"`

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   String concatenation

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   `1 + 2`

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   Integer addition

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   `"foo" == "f" + "oo"`

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   Equality test (evaluates to `true`)

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   `"foo" != "bar"`

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   Inequality test (evaluates to `true`)

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   `!true`

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   Boolean negation

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   `{ x = 1; y = 2; }.x`

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   [Attribute selection](@docroot@/language/types.md#attribute-set) (evaluates to `1`)

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   `{ x = 1; y = 2; }.z or 3`

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   [Attribute selection](@docroot@/language/types.md#attribute-set) with default (evaluates to `3`)

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   `{ x = 1; y = 2; } // { z = 3; }`

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   Merge two sets (attributes in the right-hand set taking precedence)

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   *Control structures*

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   `if 1 + 1 == 2 then "yes!" else "no!"`

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   [Conditional expression](@docroot@/language/syntax.md#conditionals).

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   `assert 1 + 1 == 2; "yes!"`

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   [Assertion](@docroot@/language/syntax.md#assertions) check (evaluates to `"yes!"`).

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   `let x = "foo"; y = "bar"; in x + y`

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Title: Nix Language Examples: Compound Values, Operators, and Control Structures
Summary
This section provides an overview of the Nix language features through examples. It covers compound values such as attribute sets (including nested and recursive sets) and lists. It also illustrates operators for string concatenation, integer addition, equality and inequality tests, boolean negation, attribute selection, merging sets, and control structures like conditional expressions and assertions. The examples demonstrate the syntax and evaluation of these features in Nix.