| attr.rs |
|
5523 |
| error.rs |
|
1350 |
| lib.rs |
[![github]](https://github.com/dtolnay/paste) [![crates-io]](https://crates.io/crates/paste) [![docs-rs]](https://docs.rs/paste)
[github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
[crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
[docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
<br>
The nightly-only [`concat_idents!`] macro in the Rust standard library is
notoriously underpowered in that its concatenated identifiers can only refer to
existing items, they can never be used to define something new.
[`concat_idents!`]: https://doc.rust-lang.org/std/macro.concat_idents.html
This crate provides a flexible way to paste together identifiers in a macro,
including using pasted identifiers to define new items.
This approach works with any Rust compiler 1.31+.
<br>
# Pasting identifiers
Within the `paste!` macro, identifiers inside `[<`...`>]` are pasted
together to form a single identifier.
```
use paste::paste;
paste! {
// Defines a const called `QRST`.
const [<Q R S T>]: &str = "success!";
}
fn main() {
assert_eq!(
paste! { [<Q R S T>].len() },
8,
);
}
```
<br><br>
# More elaborate example
The next example shows a macro that generates accessor methods for some
struct fields. It demonstrates how you might find it useful to bundle a
paste invocation inside of a macro\_rules macro.
```
use paste::paste;
macro_rules! make_a_struct_and_getters {
($name:ident { $($field:ident),* }) => {
// Define a struct. This expands to:
//
// pub struct S {
// a: String,
// b: String,
// c: String,
// }
pub struct $name {
$(
$field: String,
)*
}
// Build an impl block with getters. This expands to:
//
// impl S {
// pub fn get_a(&self) -> &str { &self.a }
// pub fn get_b(&self) -> &str { &self.b }
// pub fn get_c(&self) -> &str { &self.c }
// }
paste! {
impl $name {
$(
pub fn [<get_ $field>](&self) -> &str {
&self.$field
}
)*
}
}
}
}
make_a_struct_and_getters!(S { a, b, c });
fn call_some_getters(s: &S) -> bool {
s.get_a() == s.get_b() && s.get_c().is_empty()
}
#
# fn main() {}
```
<br><br>
# Case conversion
Use `$var:lower` or `$var:upper` in the segment list to convert an
interpolated segment to lower- or uppercase as part of the paste. For
example, `[<ld_ $reg:lower _expr>]` would paste to `ld_bc_expr` if invoked
with $reg=`Bc`.
Use `$var:snake` to convert CamelCase input to snake\_case.
Use `$var:camel` to convert snake\_case to CamelCase.
These compose, so for example `$var:snake:upper` would give you SCREAMING\_CASE.
The precise Unicode conversions are as defined by [`str::to_lowercase`] and
[`str::to_uppercase`].
[`str::to_lowercase`]: https://doc.rust-lang.org/std/primitive.str.html#method.to_lowercase
[`str::to_uppercase`]: https://doc.rust-lang.org/std/primitive.str.html#method.to_uppercase
<br>
# Pasting documentation strings
Within the `paste!` macro, arguments to a #\[doc ...\] attribute are
implicitly concatenated together to form a coherent documentation string.
```
use paste::paste;
macro_rules! method_new {
($ret:ident) => {
paste! {
#[doc = "Create a new `" $ret "` object."]
pub fn new() -> $ret { todo!() }
}
};
}
pub struct Paste {}
method_new!(Paste); // expands to #[doc = "Create a new `Paste` object"]
``` |
14959 |
| segment.rs |
|
9209 |