tutorial: clearer explanation of freezing.
- "Lending an immutable pointer" might be confusing. It was not discussed why borrowed pointers are immutable in the first place. - Make it clear that the borrowed pointers are immutable even if the variable was declared with `mut`. - Make it clear that we cannot even assign anything to the variable while its value is being borrowed. tutorial: change "--" to an em-dash. tutorial: change instances of "--" to em-dash.
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@ -1468,14 +1468,14 @@ For a more in-depth explanation of references and lifetimes, read the
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## Freezing
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Lending an immutable pointer to an object freezes it and prevents mutation.
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Lending an &-pointer to an object freezes it and prevents mutation—even if the object was declared as `mut`.
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`Freeze` objects have freezing enforced statically at compile-time. An example
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of a non-`Freeze` type is [`RefCell<T>`][refcell].
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~~~~
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let mut x = 5;
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{
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let y = &x; // `x` is now frozen, it cannot be modified
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let y = &x; // `x` is now frozen. It cannot be modified or re-assigned.
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}
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// `x` is now unfrozen again
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# x = 3;
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@ -2021,8 +2021,8 @@ C++ templates.
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## Traits
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Within a generic function -- that is, a function parameterized by a
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type parameter, say, `T` -- the operations we can do on arguments of
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Within a generic function—that is, a function parameterized by a
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type parameter, say, `T`—the operations we can do on arguments of
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type `T` are quite limited. After all, since we don't know what type
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`T` will be instantiated with, we can't safely modify or query values
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of type `T`. This is where _traits_ come into play. Traits are Rust's
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