rusty-iter-cpp

This library provides iterator functionality similar to what is available in the Rust programming language. See https://doc.rust-lang.org/std/iter/trait.Iterator.html

Usage

This is a single-file, header-only library. To use it, just include rusty-iter.hpp in your project.

All available functions are in the rusty namespace.

Creating a rusty iterator from an stl collection:

auto it = rusty::iter(collection);

Creating a rusty iterator from C++ iterators:

auto it = rusty::iter(begin, end);

Iterating over the elements of a rusty iterator:

for (const auto& value : iter) { ... }

or

iter.for_each([](const auto& value) { ... });

Using iterators (example):

rusty::iter(collection)
   .filter([](const int& value) { return value % 2 == 0; })
   .step_by(2)
   .map([](const int& value) { return value * value; })
   .collect<std::vector<int>>();

Iterators can be manually advanced by calling the .next() function on them, which will return a pointer to the next value, or a null pointer if the iterator has finished.

Documentation

See https://github.com/Kimbatt/rusty-iter-cpp/blob/master/docs/README.md

Requirements

This library requires C++17 or later.
There are no external dependencies, only the C++ standard library (type_traits, optional and the utility headers are used).

Comparison functions

When using functions that require you to specify a comparison function:
The provided comparison function must take two values and return a value that is <0 if the first value is less than the second, 0 if the two values are equal, and >0 if the first value is greater than the second.
You can return any type that can be compared this way.
When using C++20 or later, you for example can use std::strong_ordering (spaceship operator).
For partial comparisions, you need to return an std::optional value, which is empty if the values cannot be compared, otherwise just return <0, 0, or >0 (as described above).

Notes on memory safety

Unlike Rust, C++ doesn't have compile time guarantees about memory safety, so you must be careful with the following:

• The values passed to the user-provided functions are only guaranteed to be valid for the duration of that function call. For example:

// DON'T DO THIS
int* ptr = nullptr;
std::vector<int> numbers = { 1, 2, 3 };
rusty::iter(numbers).for_each([](const int& i) { ptr = &i; });
std::cout << *ptr << std::endl; // BAD, ptr is invalid

• Same for loops:

// DON'T DO THIS
int* ptr = nullptr;
std::vector<int> numbers = { 1, 2, 3 };
for (const int& i : rusty::iter(numbers))
{
    ptr = &i; // ptr becomes invalid after the current iteration
}
std::cout << *ptr << std::endl; // BAD, ptr is invalid

• Advancing the iterator after the underlying collection has been destroyed is undefined behavior. For example:

// DON'T DO THIS
for (const char& ch : rusty::iter(std::string("test")))
{
    // BAD
    // the temporary string value is already destroyed here
    // this will cause bad things
}

// DO THIS INSTEAD
std::string str = "test";
for (const char& ch : rusty::iter(str))
{
    // OK
    // the original string value still exists,
    // so the iterator is valid
}

License

Licensed under either the WTFPL or the MIT License, at your choice. See https://github.com/Kimbatt/rusty-iter-cpp/blob/master/LICENSE.txt