comparison: src/metaprogramming.rs
src/metaprogramming.rs
- changeset 90
- b3c35d16affe
- parent 75
- e9f4550cfa18
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| 25:d14c877e14b7 | 90:b3c35d16affe |
|---|---|
| 1 /*! | |
| 2 Metaprogramming tools | |
| 3 */ | |
| 4 | |
| 5 /// Reference `x` if so indicated by the first parameter. | |
| 6 /// Typically to be used from another macro. | |
| 7 /// | |
| 8 /// ```ignore | |
| 9 /// maybe_ref!(ref, V) // ➡ &V | |
| 10 /// maybe_ref!(noref, V) // ➡ V | |
| 11 /// ``` | |
| 12 #[macro_export] | |
| 13 macro_rules! maybe_ref { | |
| 14 (ref, $x:expr) => { &$x }; | |
| 15 (noref, $x:expr) => { $x }; | |
| 16 (ref, $x:ty) => { &$x }; | |
| 17 (noref, $x:ty) => { $x }; | |
| 18 } | |
| 19 | |
| 20 /// Choose `a` if first argument is the literal `ref`, otherwise `b`. | |
| 21 #[macro_export] | |
| 22 macro_rules! ifref { | |
| 23 (noref, $a:expr, $b:expr) => { $b }; | |
| 24 (ref, $a:expr, $b:expr) => { $a }; | |
| 25 } | |
| 26 | |
| 27 | |
| 28 /// Annotate `x` with a lifetime if the first parameter | |
| 29 /// Typically to be used from another macro. | |
| 30 /// | |
| 31 /// ```ignore | |
| 32 /// maybe_ref!(ref, &'a V) // ➡ &'a V | |
| 33 /// maybe_ref!(noref, &'a V) // ➡ V | |
| 34 /// ``` | |
| 35 #[macro_export] | |
| 36 macro_rules! maybe_lifetime { | |
| 37 (ref, $x:ty) => { $x }; | |
| 38 (noref, &$lt:lifetime $x:ty) => { $x }; | |
| 39 (noref, &$x:ty) => { $x }; | |
| 40 } | |
| 41 |
