Yalul born with purpose of bring be simple and have a fun while studying programming languages.

This is not a language for production systems, but a language to help everyone that wants to learn how a programming language works behind scenes in a fun way.

Table of Contents

• Development Status
• Syntax
  • print
  • basic types
  • Arithmetic and Comparison
  • Variables
  • Loop
  • Control Flow
  • Functions
• Installing
  • Linux/Mac
    • Install lib requirements
    • Running
  • Docker
  • Windows
• Development Tools
  • REPL
  • Render AST
  • Render Lex Tokens
• Developing
  • Tests
  • Lint

Development Status V1

[x] Basic structure

[x] Lexer

[x] Parser

[x] Tokens/AST Printers

[x] Interpreter

[] Documentation (WIP)

Syntax

Print

Yalul has a built-in print statement to help you while developing:

print("Hello Yalul")

Basic types

Yalul has five basic value types, boolean, float, integer, null, and string:

Integers

The most basic data type, integer represent any integer number:

Yalul v0.0.1 > 42
=> 42

Float

Floats are floating point numbers, using dots:

Yalul v0.0.1 > 3.18
=> 3.18

String

Strings represents any text, and on Yalul strings are represented around ONLY double quotes:

Yalul v0.0.1 > "Hello World" 
=> "Hello World"

Booleans

Booleans as you may imagine, represents true and false:

Yalul v0.0.1 > true
=> true
Yalul v0.0.1 > false
=> false

Null

And unfortunately Yalul has its dark side (among many others), yes we have Null types to represent the absence of any information.

Yalul v0.0.1 > null
=> null

Arithmetic and Comparison

Yalul has basic math operations +, -, * and /. It has basic comparison operators too, >, <, <=, >=, ==:

Yalul v0.0.1 > 1 + 1
=> 2
Yalul v0.0.1 > 1 - 1
=> 0
Yalul v0.0.1 > 2 * 2
=> 4
Yalul v0.0.1 > 4 / 2
=> 2.0
Yalul v0.0.1 > 2 > 1
=> true
Yalul v0.0.1 > 2 < 1
=> false
Yalul v0.0.1 > 1 <= 1
=> true
Yalul v0.0.1 > 1 >= 1
=> true
Yalul v0.0.1 > 1 == 1
=> true

Variables

To declare your variable its easy, just use def keyword, pass a name and any expression as value.

def name = "otavio"

And feel free to redefine your variable:

name = "Valadares"

Loop

To loop yalul have a while statement, that will execute a given block till the given condition is true:

def counter = 0

while(counter < 10) {
  print(counter)
  counter = counter + 1
}

Control Flow

To control your flow, yalul provides a basic if/else structure:

if (42 > 41) {
  print("If block")
} else {
  print("Else block")
}

Functions

To create functions and call it its easy too, yalul provides a nice syntax for it:

func sum(a b) {
  return a + b
}

def result = sum(41, 1)

print(result)

Installing

Linux Systems and Mac os

Clone yalul repository:

git clone https://github.com/OtavioHenrique/yalul.git

Install lib requirements

pip install -r requirements.txt

Running

Go to yalul root folder and run:

PYTHONPATH=$PATHONPATH:`pwd` bin/yalul

Example passing a file

PYTHONPATH=$PATHONPATH:`pwd` bin/yalul yalul_test.yalul

You can add your folder path to your PYTHONPATH instead of set it everytime.

Docker

Clone yalul repository:

git clone https://github.com/OtavioHenrique/yalul.git

build image

Run

docker build . -t yalul

Running

docker run -v "$PWD":/usr/src/app -w /usr/src/app yalul bin/yalul

Example passing a file

docker run -v "$PWD":/usr/src/app -w /usr/src/app yalul bin/yalul yalul_test.yalul

Windows

Clone yalul repository:

git clone https://github.com/OtavioHenrique/yalul.git

Install package requeriments(Go to your cmd):

pip install -r requirements.txt

Add Yalul to your PYTHONPATH

Access:

My Computer > Properties > Advanced System Settings > Environment Variables

Create a new environment variable with name PYTHONPATH and select yalul directory.

Run

Open CMD, go yo your yalul folder and run:

python bin\yalul

Example passing a file

python bin\yalul yalul_test.yalul

Development Tools

REPL (Everybody loves REPL)

Yalul REPL is simple and intuitive, just start it without passing any file as argument, and REPL will start:

Render Lex Tokens

Yalul has a buil-in tool to render its lex tokens generated by our code. Just use the flag --render-lex-tokens.

Example

Considering the file named yalul_test.yalul containing the fallowing code:

1 + 1

Run bin/yalul --render-lex-tokens yalul_test.yalul (Unix example), and the fallowing image will be generated:

All generated images will be placed inside yalul-renders/ folder that it will create as pdf files.

Pay attention, this tool need graphviz installed, you need to install it to use. You can find the install instructions here. Graphviz are known to have PATH problems on windows, if you are using it, manually add it to yourrr PATH.

Render AST

Yalul has a built-in tool to render its AST, available out of box. To use just use the flag --render-ast while executing a file.

Example

Considering the a file named yalul_test.yalul containing the fallowing code:

func sum(a b) {
  return a + b
}

Run bin/yalul --render-ast yalul_test.yalul (Unix example), and the fallowing image will be generated:

All generated images will be placed inside yalul-renders/ folder that it will create as pdf files.

Pay attention, this tool need graphviz installed, you need to install it to use. You can find the install instructions here. Graphviz are known to have PATH problems on windows, if you are using it, manually add it to yourrr PATH.

Developing

Tests

Yalul uses pytest as its test framework. To run it, just type:

PYTHONPATH=$PATHONPATH:`pwd` pytest

Lint

Yalul uses flake8 as python linter. By default we run the fallowing line while developing:

flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics