Merge pull request #11131 from rhendric/rhendric/pipe-operators

libexpr: experimental pipe operators

doc/manual/rl-next/pipe-operators.md

@@ -0,0 +1,28 @@
+---
+synopsis: "Add `pipe-operators` experimental feature"
+prs:
+- 11131
+---
+
+This is a draft implementation of [RFC 0148](https://github.com/NixOS/rfcs/pull/148).
+
+The `pipe-operators` experimental feature adds [`<|` and `|>` operators][pipe operators] to the Nix language.
+*a* `|>` *b* is equivalent to the function application *b* *a*, and
+*a* `<|` *b* is equivalent to the function application *a* *b*.
+
+For example:
+
+```
+nix-repl> 1 |> builtins.add 2 |> builtins.mul 3
+9
+
+nix-repl> builtins.add 1 <| builtins.mul 2 <| 3
+7
+```
+
+`<|` and `|>` are right and left associative, respectively, and have lower precedence than any other operator.
+These properties may change in future releases.
+
+See [the RFC](https://github.com/NixOS/rfcs/pull/148) for more examples and rationale.
+
+[pipe operators]: @docroot@/language/operators.md#pipe-operators

doc/manual/src/language/operators.md

@@ -26,13 +26,17 @@
 | 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         |
 
 [string]: ./types.md#type-string
 [path]: ./types.md#type-path
-[number]: ./types.md#type-float <!-- TODO(@rhendric, #10970): rationalize this -->
+[number]: ./types.md#type-float
 [list]: ./types.md#list
 [attribute set]: ./types.md#attribute-set
 
+<!-- TODO(@rhendric, #10970): ^ rationalize number -> int/float -->
+
 ## Attribute selection
 
 > **Syntax**
@@ -176,3 +180,34 @@ Equivalent to `!`*b1* `||` *b2*.
 
 [Logical implication]: #logical-implication
 
+## Pipe operators
+
+- *a* `|>` *b* is equivalent to *b* *a*
+- *a* `<|` *b* is equivalent to *a* *b*
+
+> **Example**
+>
+> ```
+> nix-repl> 1 |> builtins.add 2 |> builtins.mul 3
+> 9
+>
+> nix-repl> builtins.add 1 <| builtins.mul 2 <| 3
+> 7
+> ```
+
+> **Warning**
+>
+> This syntax is part of an
+> [experimental feature](@docroot@/contributing/experimental-features.md)
+> and may change in future releases.
+>
+> To use this syntax, make sure the
+> [`pipe-operators` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-pipe-operators)
+> is enabled.
+> For example, include the following in [`nix.conf`](@docroot@/command-ref/conf-file.md):
+>
+> ```
+> extra-experimental-features = pipe-operators
+> ```
+
+[Pipe operator]: #pipe-operators