Hi, why is a String literal mutable by default when

Question

Rust

Sudeep

Hi, why is a String literal mutable by default when

declared. But not mutable by default when passed as argument to some function?

0

04.02.2024

5 ответов

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Sudeep Автор вопроса

Vladisλav
String literals are immutable in many programming ...

For example, in main function s is not mutable, but I can pass it to the make_awesome function which needs mut String. fn main() { let s = String::from("Rust"); let s = make_awesome(s); println!("{s}") } fn make_awesome(mut s: String) -> String { s.push_str(" is awesome!"); return s }

0

2 месяца назад

Artem Starikov

Sudeep
For example, in main function s is not mutable, bu...

well, here you _move_ your string completely (i.e. give up on it completely), and make_awesome can do anything with it, including mutating it

0

2 месяца назад

Sudeep Автор вопроса

Artem Starikov
well, here you _move_ your string completely (i.e....

Then isn't it redundant to put mut in function argument (in this case)? Since it is anyway taking ownership?

0

2 месяца назад

Artem Starikov

Sudeep
Then isn't it redundant to put mut in function arg...

if you don't mark it as mutable, you won't be able to mutate it

0

2 месяца назад

Vladisλav · Accepted Answer

String literals are immutable in many programming languages. When you declare a string literal, it's not mutable by default; it's actually immutable. When you pass a string to a function, the immutability remains. If it seems mutable in some contexts, it's because many languages allow syntactic sugar to make strings appear mutable, or they provide mutable versions of string-like data structures. However, when passed as an argument, the function receives a reference or copy of the string, not the original string itself, preserving immutability.

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Hi, why is a String literal mutable by default when

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