comparison: src/metaprogramming.rs
src/metaprogramming.rs
- branch
- dev
- changeset 119
- cc0c6a8d0933
- parent 118
- 0fabd0b5914c
- child 120
- 07e487685b29
equal
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replaced
| 118:0fabd0b5914c | 119:cc0c6a8d0933 |
|---|---|
| 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_rules! maybe_ref { | |
| 13 (ref, $x:expr) => { | |
| 14 &$x | |
| 15 }; | |
| 16 (noref, $x:expr) => { | |
| 17 $x | |
| 18 }; | |
| 19 (ref, $x:ty) => { | |
| 20 &$x | |
| 21 }; | |
| 22 (noref, $x:ty) => { | |
| 23 $x | |
| 24 }; | |
| 25 } | |
| 26 | |
| 27 /// Choose `a` if first argument is the literal `ref`, otherwise `b`. | |
| 28 // macro_rules! ifref { | |
| 29 // (noref, $a:expr, $b:expr) => { | |
| 30 // $b | |
| 31 // }; | |
| 32 // (ref, $a:expr, $b:expr) => { | |
| 33 // $a | |
| 34 // }; | |
| 35 // } | |
| 36 | |
| 37 /// Annotate `x` with a lifetime if the first parameter | |
| 38 /// Typically to be used from another macro. | |
| 39 /// | |
| 40 /// ```ignore | |
| 41 /// maybe_ref!(ref, &'a V) // ➡ &'a V | |
| 42 /// maybe_ref!(noref, &'a V) // ➡ V | |
| 43 /// ``` | |
| 44 macro_rules! maybe_lifetime { | |
| 45 (ref, $x:ty) => { | |
| 46 $x | |
| 47 }; | |
| 48 (noref, &$lt:lifetime $x:ty) => { | |
| 49 $x | |
| 50 }; | |
| 51 (noref, &$x:ty) => { | |
| 52 $x | |
| 53 }; | |
| 54 } |
