# Piet interpreter
Piet is an esoteric programming language, which is based on the geometric artist Piet Mondriaan. The language specifies actions based on the transitions of colors. For a detailed explanation, please visit [the official website](https://www.dangermouse.net/esoteric/piet.html)

_Note: I used the term codel as a synonym for color block throughout the code._

## Requirements
The program requires the following libraries to be installed:
- [Python pillow](https://pillow.readthedocs.io/en/stable/), used for loading images
- [Numpy](https://numpy.org/), used for managing images
- [Pygubu](https://pypi.org/project/pygubu/), used by the GUI

## Features
This interpreter can do the following:
- Custom errors for unknown colors, unknown tokens, unknown commands and when starting in a black pixel
- Run .png images
- Run .gif images
- Output number of steps taken
- Use a Graphical User Interface:
    - Step-by-step execution of the program
        - Information about the selected codel
        - Information about the stack
        - Information about the direction
    - Visual representation of the program
    - Can open files without restarting the GUI
    - Can scale images, to better visualize the program


## Limitations
Too large images will cause the stack to overflow. The maximum size of the image is dependent on the contents.
The interpreter also can't distinguish between images with differen pixel-sizes. Due to the nature of Piet, enlarging an image will cause the interpreter to produce different results


## Parameters
The main.py file in the root directory should be used to interface with the interpreter. Each parameter that can be used will be explained here.

#### Help
The help parameter shows all parameters from the commandline, and can be set as follows
```cmd
python main.py -h
python main.py --help
```

#### File
This is a required parameter, and is a path to the image that should be interpreted. The test-images provided in the repository can be interpreted as follows:
```cmd
python main.py -f Countdown.png
python main.py --file Countdown.png

/output 
10
9
8
7
6
5
4
3
2
1

```

#### Verbose
Currently the verbose flag outputs the total amount of steps taken for the execution of the image.
```cmd
python main.py --file Countdown.py -v
python main.py --file Countdown.py --verbose

/output
10
9
8
7
6
5
4
3
2
1

Total steps: 276

```


#### Graphical
The graphical flag opens a GUI, with the given file loaded.
```cmd
python main.py --file Countdown.py -g
python main.py --file Countdown.py --graphical
```
This command should open the interface:
![countdown GUI](/Info/countdown_GUI.PNG?raw=true)


## Interpreter infographic
![infographic](/Info/poster.png?raw=true)

## Test programs:
### Add.png
This program calculates 2+2 and output it to STDOUT
### ColorError.png
This program encounters an error during lexing, and returns the full list of errors.
### Countdown.png
This program counts down from 10 to 1, outputting each number to STDOUT. This program shows how turing-complete the language is by demonstrating arithmetic functionality, boolean algebra and looping/branching.
### DivideByZero.png
This program encounters a division by zero error and prints the error to STDOUT
### Endless.png
This program loops endlessly, or until the stack overflows
### HelloWorld.png
Outputs Hello World! to STDOUT
### StackRoll.png
This program shows the functionality behind the stackroll function. It is recommended to run this in graphical mode, to show the stack changing