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82 lines
2.6 KiB
Markdown
82 lines
2.6 KiB
Markdown
# Removing Duplcation by Extracting a Function
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Generics allow us to replace specific tpyes with a placeholder that represents multiple values
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Lets look at how to remove duplication in a way that doesnt invlove generic types by extracting a function that replaces specific values with a generics.
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By being able to recognize duplicated code you can extract into a funct, you can start to recognize duplicated code that use generics
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Lets look at some code that finds the largest number in a list
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```rust
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fn main() {
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let number_list = vec![34, 50, 25, 100, 65];
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let mut largest = &number_list[0];
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for number in &number_list {
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if number > largest {
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largest = number;
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}
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}
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println!("The largest number is {largest}");
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let number_list = vec![102, 34, 6000, 89, 54, 2, 43, 8];
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let mut largest = &number_list[0];
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for number in &number_list {
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if number > largest {
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largest = number;
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}
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}
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println!("The largest number is {largest}");
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}
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```
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Although it owrks, duplicated code is tedious and error prone, also you have to update the code in multiple places when we want to change it
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To eliminate duplication you can create an abstraction by defining a function that operates on any list of integers passed in as a parameter
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This makes our code clearer
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Here is the same code by extracted into a function that finds the largest number in a `i32` list
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```rust
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fn largest(list: &[i32]) -> &i32 {
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let mut largest = &list[0];
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for item in list {
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if item > largest {
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largest = item;
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}
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}
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largest
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}
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fn main() {
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let number_list = vec![34, 50, 25, 100, 65];
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let result = largest(&number_list);
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println!("The largest number is {result}");
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let number_list = vec![102, 34, 6000, 89, 54, 2, 43, 8];
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let result = largest(&number_list);
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println!("The largest number is {result}");
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}
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```
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The parameter of the `largest` function called `list` represents any concrete slice of `i32` values that might be passed into the funct
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Here are the steps taken to change the code from the original to the second with the abstracted function:
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1. Identify duplicate code
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1. Extract the duplicated code into a function, and specify the inputs and return values of that code in the funct signature
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1. Update the two instances of dplicated code to make a call to the funct instead
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We can use these smae steps with generics to reduce code duplication, in the same way the fnction body can operate on an abstract `list` instead of specific values
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Generics allow code to operate on abstract types
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