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Explain type inference in Rust with examples.

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Type inference in Rust allows the compiler to deduce the types of variables and expressions based on their usage, without the need for explicit type annotations. Here are a few examples that illustrate how type inference works in Rust: 

1. Variable Initialization: 


        
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   let x = 42;
   let y = 3.14;
   let z = true;

In this example, Rust uses type inference to determine the types of variables `x`, `y`, and `z` based on their initial values. The type of `x` is inferred as `i32` (a 32-bit signed integer) because the initial value is an integer literal. `y` is inferred as `f64` (a 64-bit floating-point number) because the initial value is a floating-point literal. `z` is inferred as `bool` because the initial value is a boolean literal. 

2. Function Return Type Inference: 


        
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   fn add_numbers(x: i32, y: i32) -> i32 {
       x + y
   }

In this example, the function `add_numbers` takes two parameters `x` and `y`, both of type `i32`, and performs their addition. The return type of the function is not explicitly annotated, but the compiler infers it as `i32` based on the type of the addition expression `x + y`. The inferred return type ensures that the function is consistent with the declared type in the function signature. 

3. Collections and Iterators:


        
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   let fruits = vec!["apple", "banana", "orange"];
   let lengths: Vec<usize> = fruits.iter().map(|fruit| fruit.len()).collect();

In this example, we have a vector `fruits` that contains string literals. The `iter()` method is called on `fruits` to create an iterator, which is then mapped using a closure to obtain the lengths of each fruit. Finally, the `collect()` method is used to collect the mapped values into a new vector. The type of the `lengths` variable is not explicitly annotated, but the compiler infers it as `Vec<usize>` (a vector of `usize` values), based on the type returned by the `len()` method. 

4. Conditional Expressions: 


        
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   let x = 42;
   let y = if x > 10 { "greater" } else { "smaller" };

In this example, a variable `y` is assigned a value based on a conditional expression. The condition `x > 10` evaluates to either `true` or `false`. Depending on the result, the expression `"greater"` or `"smaller"` is inferred as the type of `y`. The type of `y` is deduced as `&str` (a string slice) in this case.

In all these examples, Rust's type inference analyzes the available information, such as initial values, expressions, method calls, and conditional branches, to determine the most appropriate types. This allows you to write code without explicitly annotating types, reducing verbosity while maintaining type safety. However, explicit type annotations can still be used when desired or when the inferred types need to be constrained.

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