2 stable releases
1.0.1 | Jun 28, 2020 |
---|---|
1.0.0 | Sep 13, 2019 |
#69 in #functional
Used in rcodec
10KB
132 lines
pl-hlist
This Rust library provides support for heterogeneous lists (known as HList
s). An HList
is a functional,
tuple-like, strongly-typed data structure that can contain elements of differing types.
There are three layers in this library:
- A basic
HList
data structure consisting ofHCons
andHNil
types. - An
hlist!
macro for constructing anHList
from a series of elements. - An
HListSupport
plugin/attribute that, when declared for a struct, allows for easy conversion of struct instances to/from anHList
representation.
See the next section for more details on usage of these layers.
Usage
Add a dependency to your Cargo.toml
:
[dependencies]
pl-hlist = "1.0"
Then, in your crate:
use pl_hlist::*;
An HList
can be constructed manually as follows:
let x: HCons<u8, HCons<u32, HNil>> = HCons(1u8, HCons(666u32, HNil));
The hlist!
macro provides a convenient shorthand for constructing an HList
:
let x: HCons<u8, HCons<u32, HNil>> = hlist!(1u8, 666u32);
The custom HListSupport
derive attribute can be applied to a struct declaration to automatically implement support for converting that struct to/from an HList
representation:
#[derive(HListSupport)]
struct TestStruct {
foo: u8,
bar: u32
}
let hlist0 = hlist!(1u8, 666u32);
let s = TestStruct::from_hlist(hlist0);
assert_eq!(s.foo, 1u8);
assert_eq!(s.bar, 666u32);
let hlist1 = s.into_hlist();
assert_eq!(hlist0, hlist1);
License
pl-hlist
is distributed under an MIT license. See LICENSE for more details.
Dependencies
~1.5MB
~35K SLoC