| # datafrog |
| |
| Datafrog is a lightweight Datalog engine intended to be embedded in other Rust programs. |
| |
| Datafrog has no runtime, and relies on you to build and repeatedly apply the update rules. |
| It tries to help you do this correctly. As an example, here is how you might write a reachability |
| query using Datafrog (minus the part where we populate the `nodes` and `edges` initial relations). |
| |
| ```rust |
| extern crate datafrog; |
| use datafrog::Iteration; |
| |
| fn main() { |
| |
| // Create a new iteration context, ... |
| let mut iteration = Iteration::new(); |
| |
| // .. some variables, .. |
| let nodes_var = iteration.variable::<(u32,u32)>("nodes"); |
| let edges_var = iteration.variable::<(u32,u32)>("edges"); |
| |
| // .. load them with some initial values, .. |
| nodes_var.insert(nodes.into()); |
| edges_var.insert(edges.into()); |
| |
| // .. and then start iterating rules! |
| while iteration.changed() { |
| // nodes(a,c) <- nodes(a,b), edges(b,c) |
| nodes_var.from_join(&nodes_var, &edges_var, |_b, &a, &c| (c,a)); |
| } |
| |
| // extract the final results. |
| let reachable: Vec<(u32,u32)> = variable.complete(); |
| } |
| ``` |
| |
| If you'd like to read more about how it works, check out [this blog post](https://github.com/frankmcsherry/blog/blob/master/posts/2018-05-19.md). |
| |
| ## Authorship |
| |
| Datafrog was initially developed by [Frank McSherry][fmc] and was |
| later transferred to the rust-lang-nursery organization. Thanks Frank! |
| |
| [fmc]: https://github.com/frankmcsherry |
