Quang 2.1.0

Quang

Quang is meant to be a "query" language for your tools.

Quang extends for Query Language.

You can use the language to implement filters in your applications without the need of tons of flags to your user, just provide a simple and consise integrated language and let the user build the filter himself.

So, it is at the end a "language as a lib".

There is a full playlist on youtube creating this project.

Api and language details

Does not matter what kind of query you provide as input to the evaluator, it will always return true or false. If the query is empty, it will always return true.

Data Types

Keywords

Operators

Basic syntax

Pretend we have a list of computers that have the following properties:

• Identifier
• Running
• Cors

So, we could query something like:

(running eq true and cors gte 4 and cors lte 10) or (running eq false and identifier reg 'ML-\d+') or identifier eq nil

How to Use

Let's pretend you have a list of people and you need to build a CLI to search this list.

username,age,sex,weight
user001,25,M,70.2
user002,31,F,60.7
user003,22,M,68.4
user004,29,F,55.9
user005,35,M,80.1
user006,28,F,62.5
user007,24,M,72.3
user008,30,F,59.6
user009,27,M,75.8
user010,33,F,65.2
user011,26,M,71.4
user012,32,F,63.7
user013,23,M,69.9
user014,34,F,58.3

Then, you can with a less than 20 lines of code integrate the language with your cli.

Here is a fully function example:

using Quang;

if (args.Length != 1)
{
    Console.WriteLine("Usage: dotnet run -- <search-query>");

    return;
}

string[][] content = [.. File.ReadAllLines("./logs.txt")[1..].Select(line => line.Split(','))];

var quang = new Quang.Quang(args[0])
    .Init()
    .SyntaxExpectAtom(":f")
    .SyntaxExpectAtom(":m")
    .SyntaxExpectSymbol("age", new ExpressionValueTypeInfo<IntegerExpression>())
    .SyntaxExpectSymbol("weight", new ExpressionValueTypeInfo<FloatExpression>())
    .SyntaxExpectSymbol("username", new ExpressionValueTypeInfo<StringExpression>())
    .SyntaxExpectSymbol("sex", new ExpressionValueTypeInfo<AtomExpression>());

foreach (var line in content)
{
    var username = line[0].Trim();
    var age = int.Parse(line[1]);
    var sex = line[2].ToLower().Trim();
    var weight = float.Parse(line[3]);

    var evaluator = quang.Evaluator()
        .AddStringVar("username", username)
        .AddAtomVar("sex", $":{sex}")
        .AddIntegerVar("age", age)
        .AddFloatVar("weight", weight);

    if (evaluator.Evaluate())
        Console.WriteLine($"Matched: {username},{age},{sex},{weight}");
}

In fact, this example is present here.

Then, if you run and use this filter: dotnet run -- 'sex eq :m and weight lte 70.0 and age gte 23', it should return you this:

Matched: user013,23,m,69.9

✨ Is that easy!