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Guide: Clarify that assigning/comparing different tuple types doesn't work #17836

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Oct 8, 2014
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Guide: Clarify that assigning/comparing different tuple types doesn't work #17836

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19 changes: 15 additions & 4 deletions src/doc/guide.md
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Expand Up @@ -914,12 +914,23 @@ or 'breaks up,' the tuple, and assigns the bits to three bindings.

This pattern is very powerful, and we'll see it repeated more later.

The last thing to say about tuples is that they are only equivalent if
the arity, types, and values are all identical.
There also a few things you can do with a tuple as a whole, without
destructuring. You can assign one tuple into another, if they have the same
arity and contained types.

```rust
let mut x = (1i, 2i);
let y = (2i, 3i);

x = y;
```

You can also check for equality with `==`. Again, this will only compile if the
tuples have the same type.

```rust
let x = (1i, 2i, 3i);
let y = (2i, 3i, 4i);
let y = (2i, 2i, 4i);

if x == y {
println!("yes");
Expand All @@ -928,7 +939,7 @@ if x == y {
}
```

This will print `no`, as the values aren't equal.
This will print `no`, because some of the values aren't equal.

One other use of tuples is to return multiple values from a function:

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