#![feature(slice_patterns)]
#![doc(html_root_url = "https://docs.rs/improved_slice_patterns/2.0.0")]
#[macro_export]
macro_rules! destructure_iter {
(@match_forwards, $iter:expr, ($body:expr), $x:ident.., $($rest:tt)*) => {
$crate::destructure_iter!(@match_backwards,
$iter,
({
let $x = $iter;
$body
}),
$($rest)*
)
};
(@match_forwards, $iter:expr, ($body:expr),
$variant:ident ($x:ident).., $($rest:tt)*) => {
$crate::destructure_iter!(@match_backwards,
$iter,
({
let $x = $iter
.map(|x| match x {
$variant(y) => y,
_ => unreachable!(),
});
$body
}),
$($rest)*
)
};
(@match_forwards, $iter:expr, ($body:expr), .., $($rest:tt)*) => {
$crate::destructure_iter!(@match_backwards,
$iter,
($body),
$($rest)*
)
};
(@match_forwards, $iter:expr, ($body:expr), $x:pat, $($rest:tt)*) => {
if let std::option::Option::Some($x) = $iter.next() {
$crate::destructure_iter!(@match_forwards,
$iter,
($body),
$($rest)*
)
} else {
std::option::Option::None
}
};
(@match_backwards, $iter:expr, ($body:expr), $x:pat, $($rest:tt)*) => {
$crate::destructure_iter!(@match_backwards, $iter, (
if let std::option::Option::Some($x) = $iter.next_back() {
$body
} else {
std::option::Option::None
}
), $($rest)*)
};
(@match_forwards, $iter:expr, ($body:expr) $(,)*) => {
if $iter.next().is_some() {
std::option::Option::None
} else {
$body
}
};
(@match_backwards, $iter:expr, ($body:expr) $(,)*) => {
$body
};
($iter:expr; [$($args:tt)*] => $body:expr) => {
{
#[allow(unused_mut)]
let mut iter = $iter;
$crate::destructure_iter!(@match_forwards,
iter,
(std::option::Option::Some($body)),
$($args)*,
)
}
};
}
#[macro_export]
macro_rules! match_vec {
(@make_pat; ($($acc:tt)*), $x:ident.., $($rest:tt)*) => {
$crate::match_vec!(@make_pat;
($($acc)*, $x..),
$($rest)*
)
};
(@make_pat; ($($acc:tt)*), $variant:ident ($x:ident).., $($rest:tt)*) => {
$crate::match_vec!(@make_pat;
($($acc)*, $x..),
$($rest)*
)
};
(@make_pat; ($($acc:tt)*), .., $($rest:tt)*) => {
$crate::match_vec!(@make_pat;
($($acc)*, ..),
$($rest)*
)
};
(@make_pat; ($($acc:tt)*), $x:pat, $($rest:tt)*) => {
$crate::match_vec!(@make_pat;
($($acc)*, $x),
$($rest)*
)
};
(@make_pat; (, $($acc:tt)*), $(,)*) => {
[$($acc)*]
};
(@make_pat; ($($acc:tt)*), $(,)*) => {
[$($acc)*]
};
(@make_filter; $x:ident.., $($rest:tt)*) => {
$crate::match_vec!(@make_filter;
$($rest)*
)
};
(@make_filter; $variant:ident ($x:ident).., $($rest:tt)*) => {
{
let is_all_variant = || $x.iter()
.all(|x| match x {
$variant(_) => true,
_ => false,
});
is_all_variant()
}
&&
$crate::match_vec!(@make_filter;
$($rest)*
)
};
(@make_filter; .., $($rest:tt)*) => {
$crate::match_vec!(@make_filter;
$($rest)*
)
};
(@make_filter; $x:pat, $($rest:tt)*) => {
$crate::match_vec!(@make_filter;
$($rest)*
)
};
(@make_filter; $(,)*) => {
true
};
($arg:expr; $( [$($args:tt)*] => $body:expr ),* $(,)*) => {
{
let vec = $arg;
#[allow(unused_variables, unreachable_patterns)]
match vec.as_slice() {
$(
$crate::match_vec!(@make_pat; (), $($args)*,)
if
$crate::match_vec!(@make_filter; $($args)*,)
=> {
#[allow(unused_mut)]
let mut iter = vec.into_iter();
let ret =
$crate::destructure_iter!(iter;
[$($args)*] => $body
);
match ret {
Some(x) => Ok(x),
None => unreachable!(),
}
}
)*
_ => std::result::Result::Err(vec),
}
}
};
}
#[test]
fn test() {
let test = |v: Vec<Option<isize>>| {
match_vec!(v.into_iter();
[Some(_x), None, None] => 4,
[Some(_x), None] => 2,
[None, Some(y)] => 1,
[None, _y..] => 3,
[_x.., Some(y), Some(z), None] => y - z,
[Some(ys)..] => ys.sum(),
[] => 0,
[..] => -1,
)
.unwrap()
};
assert_eq!(test(vec![Some(0), None, None]), 4);
assert_eq!(test(vec![Some(0), None]), 2);
assert_eq!(test(vec![None, Some(0)]), 1);
assert_eq!(test(vec![Some(1), Some(2), Some(5), Some(14), None]), -9);
assert_eq!(test(vec![Some(1), Some(2), Some(3), Some(4)]), 10);
assert_eq!(test(vec![None]), 3);
assert_eq!(test(vec![]), 0);
assert_eq!(test(vec![Some(0), None, Some(1)]), -1);
#[derive(Debug)]
struct Foo;
let _: (Foo, Foo) = match_vec!(vec![Some(Foo), Some(Foo)];
[Some(f1), Some(f2)] => (f1, f2),
)
.unwrap();
let _: Vec<Foo> = match_vec!(vec![Foo];
[] => "Error".to_string(),
)
.unwrap_err();
}