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33 lines
1.1 KiB
Markdown
33 lines
1.1 KiB
Markdown
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---
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minutes: 3
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---
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# Functions
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<!-- mdbook-xgettext: skip -->
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```rust,editable
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fn gcd(a: u32, b: u32) -> u32 {
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if b > 0 {
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gcd(b, a % b)
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} else {
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a
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}
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}
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fn main() {
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println!("gcd: {}", gcd(143, 52));
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}
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```
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<details>
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* Declaration parameters are followed by a type (the reverse of some programming languages), then a return type.
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* The last expression in a function body (or any block) becomes the return value. Simply omit the `;` at the end of the expression.
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The `return` keyword can be used for early return, but the "bare value" form is idiomatic at the end of a function (refactor `gcd` to use a `return`).
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* Some functions have no return value, and return the 'unit type', `()`. The compiler will infer this if the `-> ()` return type is omitted.
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* Overloading is not supported -- each function has a single implementation.
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* Always takes a fixed number of parameters. Default arguments are not supported. Macros can be used to support variadic functions.
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* Always takes a single set of parameter types. These types can be generic, which will be covered later.
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</details>
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