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An experimental and minimal Datalog implementation that compiles down to LLVM.

Eclair is a minimal Datalog (for now). It supports the following features:

• Facts containing literals
• Rules consisting of one or more clauses.
• Rules can be non-recursive, recursive or mutually recursive.

Right now it compiles to LLVM but be aware there might still be bugs.Some edge cases might not be handled yet.

Let's say we want to find out which points are reachable in a graph. We candetermine which points are reachable using the following two logical rules:

1. One point is reachable from another point, iff there is a direct edge betweenthose two points.
2. One point is reachable from another point, iff there is a third point 'z' suchthat there is a direct edge between 'x' and 'z', and between 'z' and 'y'.

The Eclair code below can be used to calculate the solution:

@def edge(u32, u32).@def reachable(u32, u32).reachable(x, y) :-  edge(x, y).reachable(x, z) :-  edge(x, y),  reachable(y, z).

The above code can be compiled to LLVM using the Docker image provided by this repo:

$ git clone git@github.com:luc-tielen/eclair-lang.git$cd eclair-lang$ docker build. -t eclair# The next line assumes the eclair code is saved as "example.dl" in the current directory$ docker run -v$PWD:/code --rm -it eclair:latest compile /code/example.dl# NOTE: output can be redirected to a file using standard shell functionality: docker run ... > example.ll

This will emit the generated LLVM IR to the stdout of the terminal. If we savethis generated LLVM IR to a file (e.g.example.ll), we can link it with thefollowing C code that calls into Eclair, using the following command:clang -o program main.c example.ll.

// Save this file as "main.c".#include<stdio.h>#include<stdlib.h>#include<stdbool.h>#include<stdint.h>structprogram;externstructprogram*eclair_program_init();externvoideclair_program_destroy(structprogram*);externvoideclair_program_run(structprogram*);externvoideclair_add_facts(structprogram*,uint16_tfact_type,uint32_t*data,size_tfact_count);externvoideclair_add_fact(structprogram*,uint16_tfact_type,uint32_t*data);externuint32_t*eclair_get_facts(structprogram*,uint16_tfact_type);externvoideclair_free_buffer(uint32_t*data);intmain(intargc,char**argv){structprogram*prog=eclair_program_init();// edge(1,2), edge(2,3)uint32_tdata[]= {1,2,2,3    };eclair_add_facts(prog,0,data,2);eclair_program_run(prog);// NOTE: normally you call btree_size here to figure out the size, but I know there are only 3 factsuint32_t*data_out=eclair_get_facts(prog,1);printf("REACHABLE: (%d, %d)\n",data_out[0],data_out[1]);// (1,2)printf("REACHABLE: (%d, %d)\n",data_out[2],data_out[3]);// (2,3)printf("REACHABLE: (%d, %d)\n",data_out[4],data_out[5]);// (1,3)eclair_free_buffer(data_out);eclair_program_destroy(prog);return0;}

If you run the resulting program, this should print the reachable node pairs(1,2),(2,3) and(1,3) to the screen!

• LSP support
• Allow setting options on relations for performance finetuning
• Comparison operators, != operator
• Support arithmetic operators
• Generic, extensible primops
• Support logical negation
• Release 0.2.0
• Signed integer type (i32)
• Unary negation
• Optimizations on the AST / RA / LLVM level
• Support other underlying data structures than btree
• Syntactic sugar (disjunctions in rule bodies, multiple rule heads, ...)
• Support Datalog programs spanning multiple files
• ...

This roadmap is not set in stone, but it gives an idea on the direction of theproject. 😄

Contributions are welcome! Take a look at thegetting started guide on how to set up your machineto build, run and test the project. Once setup, the Makefile contains the mostcommonly used commands needed during development.

You can also use theDockerfile in this repository if you want to experimentwith Eclair without installing the toolchain yourself. You can do that asfollows:

$ docker build -f Dockerfile. -t eclair$ touch test.eclair# Here you can put your Eclair code$ docker run -v$PWD:/code --rm -it eclair eclair compile /code/test.eclair

Take a look at ourdocs folder for more information about Eclair.

Eclair is inspired bySoufflé, a highperformance Datalog that compiles to C++. Because of the similarities, I chose adifferent kind of food that I like. I mean, an eclair containsboth chocolate andpudding, what's not to like!?

Logo art byBruno Monts,with special thanks to theFission team.Please contact Luc Tielen before using the logo for anything.