https://github.com/emadb/recursionex
https://github.com/emadb/recursionex
Last synced: over 1 year ago
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- Host: GitHub
- URL: https://github.com/emadb/recursionex
- Owner: emadb
- Created: 2023-12-09T18:03:37.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2024-03-14T16:44:15.000Z (over 2 years ago)
- Last Synced: 2025-02-05T05:29:35.239Z (over 1 year ago)
- Language: Elixir
- Size: 22.5 KB
- Stars: 0
- Watchers: 2
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Let's talk about recursion
- Recursion is a method where the solution to a problem depends on solutions to smaller instances of the same problem.
- Some mathematical samples are intriscly recursive: Fact(n) = n * Fact(n - 1), Fact(1) = 1
- Structure of Recursive Functions
Base Case: A condition that stops the recursion, preventing infinite loops.
Recursive Step: A part of the function that calls itself with a simpler or smaller argument.
- The Rationale Behind Using Recursion
Ideal for Complex Problems: "Simplifies coding complex problems like tree traversals."
Aligns with Functional Programming: "Recursion is a natural fit for Elixir's functional programming style."
- Benefits
Simplicity: Recursion can turn complex algorithms into clearer, more manageable code (tree traversals)
Readability and Maintainability: Recursive solutions can be more intuitive and easier to follow (declarative vs imperative)
Reducing State Management Complexity: Iteration often requires manual tracking of state, which recursion handles naturally.
Recursion complements the stateless and immutable nature of functional programming
TCO allows recursion to be as memory efficient as iteration
- Pitfalls
Stack overflow
Performance (memory consumption)
Debugging
- Conceptual differences with iterations:
Recursion: "Focuses on breaking down a problem into simpler instances of itself."
Iteration: "Relies on a loop construct to repeat an operation until a condition is met."
- Advanced cases
Mutual recursion: is_even/1 is_odd/1
Accumulative Recursion (TOC Factorial)
- TOC
```
defmodule Factorial do
def calculate(n), do: factorial_acc(n, 1)
defp factorial_acc(0, acc), do: acc
defp factorial_acc(n, acc) when n > 0, do: factorial_acc(n - 1, n * acc)
end
```
```
defmodule Factorial do
def calculate(0), do: 1
def calculate(n) when n > 0, do: n * calculate(n - 1)
end
```
## The Rules
1) When recurring on a list ask two questions about it?
null?(list)/empty?(list) and else
2) Always change 1 argument while recurring. It must be change to be closer to the termination. The changing argument must be tested in the termination condition.
## Esempi
- size
- sum
- first
- last
- member?
- remove_first
- remove_all
- replace
- map
- reduce
- max (using reduce)
- all? (using reduce)
- reverse
- zip
Lodash
- index_of
- filter
- sort_by
- find
- value (operazioni matematiche)
- Maze example
- Sorting
- Tree traversing
- Split (even and odd)