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...In the example below, the straightforward match statement leads to code that is overall more cumbersome.
use std::num::ParseIntError;
// With the return type rewritten, we use pattern matching without `unwrap()`.
fn multiply(first_number_str: &str, second_number_str: &str) -> Result<i32, ParseIntError> {
match first_number_str.parse::<i32...
...Adding this hint to enums will force downstream crates to add a wildcard arm to
`match` statements, ensuring that adding new variants is not a breaking change.
Adding this hint to structs or enum variants will prevent downstream crates
from constructing or exhaustively matching, to ensure that adding new fields...
pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<'_, T, F>slice::splitn_mut — Returns an iterator over mutable subslices separated by elements that match pred, limited to returning at most n items. The matched element is not contained in the subslices.
The last element returned, if any, will contain the remainder of the slice.
Examples
let mut v = [10, 40...
...When you press Enter, matching lines go to stdout. Non-TTY stdout skips the TUI entirely, so it composes in pipelines. The --json <PATH> flag extracts a specific field from JSONL records before matching — useful when you want to filter by message content without the pattern accidentally matching timestamps or...
...I have extended the shorthand syntax for matching against containers in the verify_that! macro
and friends to other macro-based matchers, such as matches_pattern!. So one can write things
like:
matches_pattern!(MyStruct { a_vec: [eq(1), eq(2), eq(3)] })
The type alias Result is now called...
Guards
A match guard can be added to filter the arm.
#[allow(dead_code)]
enum Temperature {
Celsius(i32),
Fahrenheit(i32),
}
fn main() {
let temperature = Temperature::Celsius(35);
// ^ TODO try different values for `temperature`
match temperature {
Temperature::Celsius(t) if t > 30 => println!("{}C is above 30 Celsius", t),
// The `if...
...The macro is called matching!:
matching!(1, "2", 3.0)
It basically expands to a pattern match on the arguments, along with useful diagnostics in the case of an unsuccessful match.
Every string literal is matched using AsRef<str>.
The input matching was not the hardest part to design.
Now...
pub fn rmatches<P>(&self, pat: P) -> RMatches<'_, P>str::rmatches — Returns an iterator over the disjoint matches of a pattern within this string slice, yielded in reverse order.
The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.
Iterator behavior
The returned iterator requires that the...
pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<'_, T, F>slice::rsplitn_mut — Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.
The last element returned, if any, will contain the...
...Notice we no longer can use &self.xxx in our field args, instead we need to use the values from the match arms.
Pattern matching
So, a neat thing of rust is that you can use patterns outside of match statements. Take a look at this
Now, wouldn't you...
...assert!(specific.eval(|pred| { match pred { Predicate::Target(tp) => tp.matches(x86_win), Predicate::TargetFeature(feat) => avail_target_feats.contains(feat), Predicate::Feature(feat) => *feat == "cool_thing", _ => false, } })); // This will *not* satisfy the vendor predicate assert!(!specific.eval(|pred| { match pred { Predicate::Target(tp) => tp.matches(uwp_win), Predicate::TargetFeature...
pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<'_, T, F>slice::rsplitn — Returns an iterator over subslices separated by elements that match pred limited to returning at most n items. This starts at the end of the slice and works backwards. The matched element is not contained in the subslices.
The last element returned, if any, will contain the remainder...
pub fn rfind<P>(&self, pat: P) -> Option<usize>str::rfind — Returns the byte index for the first character of the last match of the pattern in this string slice.
Returns None if the pattern doesn't match.
The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character...
...FnOnce(PathElems) -> T
function, which I will use to match the path. Since I suspect this
is something we intend to do in other lints, too, I’m going to put this
matching function in
utils.rs
as fn match_def_path(cx: Context, def_id: DefId, path: &[&str]) -> bool...
...Some(vec![]),
};
let x = Some(42);
match x {
Some(x)
if let A { related_points, .. } = a
&& let Some(points) = related_points => points.len()
_ => 1,
};
}
So, currently you are forced to write a block like this
match x {
Some(x) => {
if let A { related_points, .. } = a
&& let Some(points) = related_points...
...MyUnion) {
unsafe {
match u {
MyUnion { f1: 10 } => { println!("ten"); }
MyUnion { f2 } => { println!("{}", f2); }
}
}
}
```
Matching a specific value from a union field makes a refutable pattern; naming
a union field without matching a specific value makes an irrefutable pattern.
Both require unsafe code.
Pattern matching may match a union as a...
...char) -> ((), u8) {
match op {
'+' | '-' => ((), 5),
_ => panic!("bad op: {:?}", op),
}
}
fn postfix_binding_power(op: char) -> Option<(u8, ())> {
let res = match op {
'!' => (7, ()),
_ => return None,
};
Some(res)
}
fn infix_binding_power(op: char) -> (u8, u8) {
match op {
'+' | '-' => (1, 2),
'*' | '/' => (3, 4),
'.' => (10, 9),
_ => panic!("bad op: {:?}"),
}
}
#[test]
fn tests() {
let s...
...The match code is 5 instructions longer than the lookup code — that’d explain things if match were consistently slower than lookup, but that’s not the case — match is only slower in the “mix with rotate” task for 4 and 8 letter alphabets.
It’s also worth noting that...
...let if_else_regex = Regex::new(r"\{% if (.*?) %\}((.|\n)*?)(\{% else %\}((.|\n)*?)\{% endif %\}|\{% endif %\})").unwrap();
RegEx Breakdown
{% if — Match first part of opening tag
(.*?) — Match any text lazily
%} — Match end part of opening tag
((.|\n)*?) — Match multi-line string of text lazily
{% else %} — Match else tag
((.|\n)*?) — Match multi-line string...
...previous borrow of `*self` occurs here; the mutable
borrow prevents subsequent moves, borrows, or
modification of `*self` until the borrow ends
<anon>:16 match self.find_thing_mut(name) {
^~~~
<anon>:24:10: 24:10 note: previous borrow ends here
<anon>:16 match self.find_thing_mut(name) {
...
<anon>:24 }
^
<anon...
"In #rustlang, None is always an Option<\_>."