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@@ -248,6 +248,8 @@ fn frbonicate(f: impl AsRef<Path>) {
248 248
249# Premature Pessimization 249# Premature Pessimization
250 250
251## Avoid Allocations
252
251Avoid writing code which is slower than it needs to be. 253Avoid writing code which is slower than it needs to be.
252Don't allocate a `Vec` where an iterator would do, don't allocate strings needlessly. 254Don't allocate a `Vec` where an iterator would do, don't allocate strings needlessly.
253 255
@@ -267,6 +269,8 @@ if words.len() != 2 {
267} 269}
268``` 270```
269 271
272## Push Allocations to the Call Site
273
270If allocation is inevitable, let the caller allocate the resource: 274If allocation is inevitable, let the caller allocate the resource:
271 275
272```rust 276```rust
@@ -282,6 +286,9 @@ fn frobnicate(s: &str) {
282} 286}
283``` 287```
284 288
289This is better because it reveals the costs.
290It is also more efficient when the caller already owns the allocation.
291
285## Collection types 292## Collection types
286 293
287Prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`. 294Prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`.