标签 rust
<分区>
我可以在 Debug 中打印以下数组:
fn main() {
let array = [0; 5];
println!("{:?}", array);
}
但是，如果大小更大，假设为 50，则默认不会实现 std::fmt::Debug 特性:
fn main() {
let array = [0; 50];
println!("{:?}", array);
}
编译错误:
error[E0277]: the trait bound
[{integer}; 50]: std::fmt::Debugis not satisfied
为什么 std::fmt::Debug 特性没有为某些大小的数组实现？
最佳答案
来自 https://doc.rust-lang.org/std/primitive.array.html :
Arrays of sizes from 0 to 32 (inclusive) implement the following traits if the element type allows it:
- Clone (only if T: Copy)
- Debug
- IntoIterator (implemented for &[T; N] and &mut [T; N])
- PartialEq, PartialOrd, Eq, Ord
- Hash
- AsRef, AsMut
- Borrow, BorrowMut
- Default
This limitation on the size N exists because Rust does not yet support code that is generic over the size of an array type. [Foo; 3] and [Bar; 3] are instances of same generic type [T; 3], but [Foo; 3] and [Foo; 5] are entirely different types. As a stopgap, trait implementations are statically generated up to size 32.
Arrays of any size are Copy if the element type is Copy. This works because the Copy trait is specially known to the compiler.
关于rust - 为什么 "large"数组没有实现 std::fmt::Debug？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41162696/