Doublets

Example

```rust,no_run // alpha does not has human prelude use doublets::{ data::Flow::{Break, Continue}, // also can use std::ops::ControlFlow doublets::mem::united, doublets::Doublets, mem::FileMappedMem, }; use std::error::Error;

fn main() -> Result<(), Box> { // A doublet links store is mapped to "db.links" file: let mem = FileMappedMem::new("db.links")?; let mut links = united::Store::::new(mem)?;

// A creation of the doublet link:
let link = links.create()?;

// The link is updated to reference itself twice (as a source and a target):
let link = links.update(link, link, link)?;

println!("The number of links in the data store is {}", links.count());
println!("Data store contents:");

links.try_each(|link| {
    println!("{}", link);
    Continue
});

// The link's content reset:
let link = links.update(link, 0, 0)?;

// The link deletion:
links.delete(link)?;
Ok(())

} ```