Examples

This directory contains examples of how to use the library from the different languages we support (other than C++. For C++ examples see the tests or tools directories).

At the moment we support C, C++, Rust, Python, and dotnet. The C API has been designed to make it straightforward to wrap for other languages. To see some examples, look at the wrappers directory.

C++

You can begin by looking at example.cc to see some sample usage of the API. custom_builtin.cc shows how to add your own custom builtins (only supported in C++ at this point in time).

From there, the best way to get a more in-depth understanding of the C++ API is to look at the rego tool.

C

There are two C examples. The first, example.c exercises the C API, showing all the various ways it can be used. The second C example is a command line tool that takes one or more Rego data, module, and input files and evaluates a query against them.

To build it on Linux:

a@host:rego-cpp$ cd examples/c
a@host:c$ mkdir build
a@host:c$ cd build
a@host:build$ cmake .. --preset release-clang
a@host:build$ ninja install

and on Windows:

cd examples\c
mkdir build
cd build
cmake .. --preset release
cmake --build . --config Release --target INSTALL

The resulting executable can be called from within the dist directory:

a@host:build$ cd dist
a@host:dist$ ./bin/regoc -d examples/scalars.rego -q data.scalars.greeting
{"expressions":["Hello"]}

Python

The Python example is a demonstration program that shows how to use all the features of the wrapper, including queries, input/data, and bundles.

a@host:python$ pip install regopy
a@host:python$ python example.py
Query Only
{"expressions":[true, true, 10], "bindings":{"x":5, "y":9.4}}
x = 5
10
 
Input and Data
{"expressions":[true], "bindings":{"x":[{"bar":"Foo", "baz":5, "be":true, "bop":23.4},"20",{"name":"smoke1"}]}}
 
Bundles
query: {"expressions":[true], "bindings":{"x":4460}}
example/foo: {"expressions":[2275]}

There is also a command line tool that takes zero or more Rego data, module, and input files and evaluates a query against them.

Rust

The Rust example is a demonstration program that shows how to use all the features of the wrapper, including queries, input/data, and bundles.

a@host:rust$ cargo run
Query Only
{"expressions":[true, true, 10], "bindings":{"x":5, "y":9.4}}
x = 5
10
 
Input and Data
{"expressions":[true], "bindings":{"x":[{"bar":"Foo", "baz":5, "be":true, "bop":23.4},"20",{"name":"smoke1"}]}}
 
Bundles
query: {"expressions":[true], "bindings":{"x":4460}}
example/foo: {"expressions":[2275]}

dotnet

The dotnet example does not provide a full command-line tool, but it does show how use all the features of the wrapper:

a@host:dotnet$ dotnet run
Query Only
{"expressions":[true, true, 10], "bindings":{"x":5, "y":9.4}}
x = 5
10
 
Input and Data
{"expressions":[true], "bindings":{"x":[{"bar":"Foo", "baz":5, "be":true, "bop":23.4},"20",{"name":"smoke1"}]}}
 
Bundles
query: {"expressions":[true], "bindings":{"x":4460}}
example/foo: {"expressions":[2275]}