list-fn

A generic lazy list. It's an immutable iterator with continuations.

The lazy list can be used as an immutable alternative to the standard Rust iterator.

Any List<End = Self> is an iterator. Any &mut Iterator is a List<End = Self>.

See also Generators.

Fundamental Operations

• FlatScan. An order of items is important.
  • FilterScan
  • Scan
  • Fold
• FlatMap. An order of items is not important.
  • Map
  • Filter
  • Flatten

Evolution

1. Iterator

```rust trait Iterator { type Item; fn next(&mut self) -> Option; }

trait IteratorReturn: Iterator { type Return; fn return(&mut self) -> Return; } ```

2. Generator

```rust trait Generator { type Yield; type Return; fn resume(&mut self) -> GeneratorState; }

enum GeneratorState { Yielded(Y), Complete(R), } ```

3. List

```rust trait List { type Yield; type Return; fn resume(self) -> ListState; }

enum ListState { Yielded(L::Yield, L), Return(L::Return), } ```

FlatScan

3. List

rust trait FlatScan { type InputYield; type InputReturn; type OutputYield; type OutputReturn; fn map_yield(self, input_yield: Self::InputYield) -> impl List<Yield = Self::OutputYield, Return = Self>; fn map_return(self, input_return: Self::InputReturn) -> impl List<Yield = Self::OutputYield, Return = OutputReturn>; }

2. Generator

rust trait FlatScan { type InputYield; type InputReturn; type OutputYield; type OutputReturn; fn map_yield(&mut self, input_yield: Self::InputYield) -> impl Iterator<Item = Self::OutputYield>; fn map_return(&mut self, input_return: Self::InputReturn) -> impl Generator<Item = Self::OutputYield, Return = Self::OutputReturn>; }

1. Iterator

rust trait FlatScan { type InputYield; type InputReturn; type OutputYield; type OutputReturn; fn map_yield(&mut self, input_yield: Self::InputYield) -> impl Iterator<Item = Self::OutputYield>; fn map_return(&mut self, input_return: Self::InputReturn) -> impl Iterator<Item = Self::OutputYield> + IteratorReturn<Return = Self::OutputReturn>; }