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https://github.com/lefticus/lambda_coroutines
A lightweight macro-based coroutine / resumable / cooperative multitasking function utility designed for C++14 lambdas.
https://github.com/lefticus/lambda_coroutines
coroutines lambdas
Last synced: about 8 hours ago
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A lightweight macro-based coroutine / resumable / cooperative multitasking function utility designed for C++14 lambdas.
- Host: GitHub
- URL: https://github.com/lefticus/lambda_coroutines
- Owner: lefticus
- License: unlicense
- Created: 2020-08-28T04:10:34.000Z (about 4 years ago)
- Default Branch: main
- Last Pushed: 2020-08-30T20:09:51.000Z (about 4 years ago)
- Last Synced: 2024-06-12T03:02:29.957Z (5 months ago)
- Topics: coroutines, lambdas
- Language: CMake
- Homepage:
- Size: 43.9 KB
- Stars: 37
- Watchers: 5
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
- License: LICENSE
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README
# Lambda Coroutines
[](https://codecov.io/gh/lefticus/lambda_coroutines)
## Description
A lightweight macro-based coroutine / resumable / cooperative multitasking function utility designed for C++14 lambdas.
# Examples
## Rotating Infinite Sequence
```cpp
// lambda must be mutable
auto next_direction = [state=0]() mutable {
// set up coroutine, needs a captured integral `state` value
lambda_co_begin(state);
// for eternity yeild the next possible value
while (true) {
lambda_co_yield(directions::Left);
lambda_co_yield(directions::Right);
lambda_co_yield(directions::Up);
lambda_co_yield(directions::Down);
}
lambda_co_end();
};
int main() {
auto val1 = next_direction(); // returns Left
auto val2 = next_direction(); // returns Right
// etc
}
```
## Obligatory Fibonacci Sequence
```cpp
// generates the set of all fibonacci numbers representable by a ull, returns
// empty optional at end of list
auto fib = [state = 0, fib_2 = 0ULL, fib_1 = 1ULL]() mutable -> std::optional {
lambda_co_begin(state);
lambda_co_yield(0);
lambda_co_yield(1);
while (fib_1 < std::numeric_limits::max() / 2) {
fib_2 = std::exchange(fib_1, fib_2 + fib_1);
lambda_co_yield(fib_1);
}
lambda_co_return({});
};
```
## Ranged `for` Statement With Coroutine
```cpp
// Using the Obligatory Fibonacci Sequence
fmt::print("All possible Fib numbers representable by 'unsigned long long'");
for (const auto value : lambda_coroutines::while_has_value(fib)) {
fmt::print("{}\n", value);
}
```
## CPU Instruction Decoding State Machine
[Compiler Explorer playground](https://godbolt.org/z/7dr8j7) for this example.
```cpp
enum OpCodes : std::uint8_t {
ADD = 0,
STA = 1,
NOP = 2
};
struct Machine {
std::uint8_t PC{0};
std::uint8_t A{0};
std::array RAM{STA, 10, ADD, 15};
};
Machine machine;
auto CPU = [state = 0, &machine, op = OpCodes::NOP]() mutable {
lambda_co_begin(state);
while(true) {
op = static_cast(machine.RAM[machine.PC]);
++machine.PC;
if (op == OpCodes::STA) {
lambda_co_yield();
machine.A = machine.RAM[machine.PC++];
lambda_co_yield();
} else if (op == OpCodes::ADD) {
lambda_co_yield();
machine.A += machine.RAM[machine.PC++];
lambda_co_yield();
} else if (op == OpCodes::NOP) {
lambda_co_yield();
};
}
lambda_co_end();
};
```
# Limitations
* Cannot use `switch` statements in coroutine code
* Cannot declare variables in coroutine code
* Anything you care about must be part of the lambda capture declaration
# Using In Your Project
It is one VERY simple header file https://github.com/lefticus/lambda_coroutines/blob/main/include/lambda_coroutines/lambda_coroutines.hpp