Rust Search
Find the best content on Rust, curated by the community; a
search engine for Rustaceans.
...And we matched on it:
let regex = match Regex::new(pattern) {
Ok(r) => r,
Err(e) => {
eprintln!("Invalid pattern: {}", e);
std::process::exit(1);
}
};
Now we're going to go much deeper.
Pattern Matching on Result
Just like Option, you can match on Result:
match result {
Ok(value) => println!("success...
...On floats are raw pointers, pattern matching behaves like `==`,
which means in particular that the value `-0.0` matches the pattern `0.0`, and NaN values match no pattern (except for wildcards).
### Breaking changes
This RFC breaks code that compiles today, but only code that already emits a future compatibility...
...maybe_label FOR top_pat IN expr_nostruct block ;
```
For `match` expressions we now have:
```rust
expr_match : MATCH expr_nostruct '{' match_clause* nonblock_match_clause? '}' ;
match_clause : nonblock_match_clause ',' | block_match_clause ','? ;
nonblock_match_clause : match_arm (nonblock_expr | block_expr_dot) ;
block_match_clause : match_arm (block...
Table of ContentsThe “Error Handling” seriesLibrary vs application needsDon’t use one big enum for everythingModularityPrecise signaturesFlat vs nested enumsFlat enumsNested enumsWorkarounds for pattern matching nested enumsOther tipsWhen to reuse an error type between multiple functionsWhere to put error typesDon’t create one-variant enumsnon_exhaustiveNaming error variantsPrivacy of fieldsMixing...
Let’s say you need to match the same regex across a large number of strings – perhaps you’re applying a grep-like filter to data generated or received by your program. This toy example demonstrates it by matching a regex against half a billion strings:
use regex::Regex;
lazy...
...Key) -> &'static str {
use Key::*;
match *LANG {
Lang::En => match key {
battery_remaining => "remaining",
no_adapter_found => "No headphone adapter found",
view_logs => "View logs",
view_updates => "View updates",
quit_program => "Close",
device_charging => "(Charging)",
device_disconnected => "(Disconnected)",
version => "Version",
},
Lang::Fi => match key {
battery_remaining => "jäljellä",
no_adapter_found...
## Summary
Change pattern matching on an `&mut T` to `&mut <pat>`, away from its
current `&<pat>` syntax.
## Motivation
Pattern matching mirrors construction for almost all types, *except*
`&mut`, which is constructed with `&mut <expr>` but destructured with
`&<pat>`. This is almost certainly an unnecessary inconsistency.
This can and does lead...
...Exact match search The method finds a value associated with an exact match key as a Option . Requirements Rust version >= 1.58.0 Usage See also example code for more details. Build a double-array trie use yada::builder::DoubleArrayBuilder; // make a keyset which have key-value pairs let keyset...
...SSR now matches paths based on whether they resolve to the same thing instead of whether they’re written the same.
So foo() won’t match foo() if it’s a different function foo(), but will match bar::foo() if it’s the same foo.
Paths in the replacement will...
...An individual
`#[cfg(...)]` attribute "matches" if *all* of the contained cfg patterns match
the compilation environment, and an item preserved if it *either* has no
`#[cfg(...)]` attributes or *any* of the `#[cfg(...)]` attributes present
match.
This is problematic for several reasons:
* It is excessively verbose in certain situations. For example...
...The type of the body is `!` which matches the return type.
}
fn not_diverging() -> ! {
// This type is uninhabited.
// However, the entire function is not considered diverging.
make_empty();
// ERROR: The type of the body is `()` but expected type `!`.
}
[!NOTE] Divergence can propagate to the surrounding block. See [expr.block.diverging...
...builder.push("🍣", 7); let mut trie = builder.build(); // exact_match(): Find a word exactly match to query. assert_eq!(trie.exact_match("すし"), Some(&6)); assert_eq!(trie.exact_match("🍣"), Some(&7)); assert_eq!(trie.exact_match("🍜"), None); // Values can be modified. let v = trie.exact_match_mut("🍣").unwrap(); *v...
...Option<AttributeIndex>,
filter: &TextFilter,
) -> HashMap<EntryIndex, f64> {
let matching_terms = match filter {
TextFilter::StartsWith { prefix } => self.trienodes().search(prefix),
TextFilter::Matches { value } => self.trigrams().search(value),
TextFilter::Equals { value } => self.inner.get_term(value).into_iter(),
};
let matching_entries = self.reduce_matches(attribute, matching_terms)
self.compute_scores(attribute, matchings...
...For example, match is a keyword. If you try to compile the following function that uses match as its name:
Filename: src/main.rs
fn match(needle: &str, haystack: &str) -> bool {
haystack.contains(needle)
}
you’ll get this error:
error: expected identifier, found keyword `match`
--> src/main.rs:4:4...
...Understanding wildcards
Wildcard pattern matching allows users to employ an asterisk (*) in a string to match certain patterns. For example, a single pattern like https://example.com/*/t*st can cover multiple URLs such as https://example.com/en/test, https://example.com/images/toast, and https://example.com/blog...
...Specifically,
the syntax
```rust
['ident:] while let PAT = EXPR {
BODY
}
```
desugars to
```rust
['ident:] loop {
match EXPR {
PAT => BODY,
_ => break
}
}
```
Just as with `if let`, an irrefutable pattern given to `while let` is considered an error. This is
largely an artifact of the fact that the desugared `match` ends up...
...This is a counterpart to if let expressions, and the pattern matching works identically, except that the value from the pattern match
is assigned to the surrounding scope rather than the block’s scope.
Reference-level explanations
let-else is syntactical sugar for match where the non-matched case diverges...
introduction
logical and
logical or
if let-evaluation ordering
closing words
Introduction
One of the things that stands out to me is how similar match and if..else
are semantically, while being diverging a fair bit syntactically. The reasons for that seem mostly accidental, and I have a sneaking suspicion...
...x/re/ for each match of re, run the expressions that follow
y/re/ between each match of re, run the expressions that follow
g/re/ if re matches, run the expressions that follow
v/re/ if re does not match, run the expressions that follow
For actions, the argument...
...To add a literal ] do "[]abc]" {e} = doesn't return a value, but matches end of line. Use this if you don't want to ignore potential extra characters at end of input. Examples: {[0-9ab]} = match 0-9 or a or b {[^,.]} = match anything but , or . {/.../} = return regex inside...
"Since it hasn't been said before, there is an important distinction that needs to be addressed. For anyone who has been doing embedded work for any le..."