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Improve clarity of paragraph in the pointer guide #21031

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Jan 16, 2015
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Improve clarity of paragraph in the pointer guide #21031

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9 changes: 4 additions & 5 deletions src/doc/trpl/pointers.md
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Expand Up @@ -721,11 +721,10 @@ fn main() {
This gives you flexibility without sacrificing performance.

You may think that this gives us terrible performance: return a value and then
immediately box it up ?! Isn't that the worst of both worlds? Rust is smarter
than that. There is no copy in this code. `main` allocates enough room for the
`box`, passes a pointer to that memory into `foo` as `x`, and then `foo` writes
the value straight into that pointer. This writes the return value directly into
the allocated box.
immediately box it up ?! Isn't this pattern the worst of both worlds? Rust is
smarter than that. There is no copy in this code. `main` allocates enough room
for the `box`, passes a pointer to that memory into `foo` as `x`, and then
`foo` writes the value straight into the `Box<T>`.

This is important enough that it bears repeating: pointers are not for
optimizing returning values from your code. Allow the caller to choose how they
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