I’m still here! And less sick now.

Last time(s), we described and lexed) Runelang! This time around, let’s take the lexed tokens and go one step further and parse them!

So, how do we go about this? With a recursive descent parser!

• Start with a list/stream of tokens
• Using the first k (in a LL(k) parser) elements of the list, identify which sort of object we are parsing (a group / identifier / literal / expression / etc)
• Call a parsing function for that object type (parseGroup etc) that will:
  • Recursively parse the given object type (this may in turn call more parse functions)
  • Advance the token stream ‘consuming’ any tokens used in this group so the new ‘first’ element is the next object

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Let’s LEX!

So this is actually one of the easier parts of a programming language. In this case, we need to turn the raw text of a program into a sequence of tokens / lexemes that will be easier to parse. In this case, we want to:

• Remove all whitespace and comments
• Store the row and column with the token to make debugging easier

So let’s do it!

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Previously, I wrote a post about making a DSL in Ruby that could render magic circles/runes. It worked pretty well. I could turn things like this:

rune do
    scale 0.9 do 
        circle
        polygon 7
        star 14, 3
        star 7, 2
        children 7, scale: 1/8r, offset: 1 do |i|
            circle
            invert do
                text (0x2641 + i).chr Encoding::UTF_8
            end
        end
    end
    scale 0.15 do
        translate x: -2 do circle; moon 0.45 end
        circle
        translate x: 2 do circle; moon 0.55 end
    end
end

Into this:

But… I decided to completely rewrite it. Now it’s an entirely separate language:

Output

Source

Log (most recent messages first):

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Okay. A random post on the /r/cellular_automata subreddit inspired me.

Let’s generate a cellular automata where each pixel updates based on a neural network given as input:

• The x/y coordinates (scaled to the range 0-1)
• An optional random value (to make it more dynamic)
• A variety of neighboring data, such as:
  • The number of neighbors that are ‘active’ (> 50% white), ranges 0-8 scaled to 0-1. This should allow Conway’s Game of Life
  • The RGB values of all neighbors (allows a superset of the above)
  • Gradients, subtract color value of the left from the right so that you get edges and side to side movement

Let’s do it!

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L-Systems are pretty awesome. With only a bare few rules, you can turn something like this:

LSystem.new("Barnsley Fern") do
    start "+++X"

    rule "X", "F+[[X]-X]-F[-FX]+X" 
    rule "F", "FF"

    terminal "F" do forward end
    terminal "[" do push end
    terminal "]" do pop end
    terminal "-" do rotate -25 end
    terminal "+" do rotate +25 end
end

Into this:

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Let’s make magic circles/runes!

Turn this:

rune do
    scale 0.9 do 
        circle
        polygon 7
        star 14, 3
        star 7, 2
        children 7, scale: 1/8r, offset: 1 do |i|
            circle
            invert do
                text (0x2641 + i).chr Encoding::UTF_8
            end
        end
    end
    scale 0.15 do
        translate x: -2 do circle; moon 0.45 end
        circle
        translate x: 2 do circle; moon 0.55 end
    end
end

Into this:

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The fine people of /r/generative / Genuary2021 have a series of challenges for generative works for the month of January. I don’t think I’m going to do all of them, but pick and choose. For example, the very first prompt is:

// TRIPLE NESTED LOOP

My goal was to draw a grid of circles across the X/Y the image and nest them for the third dimension. To make it a little more interesting, I added a few different color modes. seededRandom is my personal favorite, that was interesting to get working.

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Much like transpiling register machines, now we have a chance to transpile stack machines. Unfortunately, it doesn’t actually speed up the code nearly so much (the stack is just not as effective of a memory structure in this case), but it’s still an interesting bit of code.

In this case, we turn something like this:

invsub
polT
writeG
id
neg
zero?
sin
invsub
ZERO
inv

Into this:

function(X, Y) {
  this.x = X;
  this.y = Y;

  this.stack = [];
  this.r = undefined;
  this.g = undefined;
  this.b = undefined;

  this.stack.push(X);
  this.stack.push(Y);

  var arg0 = 0;
  var arg1 = 0;
  var arg2 = 0;
  var result = 0;

  // invsub
  arg0 = this.stack.pop() || 0;
  result = 1 - arg0;
  result = result % 1.0;
  this.stack.push(result);

  // polT
  arg0 = this.stack.pop() || 0;
  arg1 = this.stack.pop() || 0;
  result = Math.atan2(arg0, arg1);
  result = result % 1.0;
  this.stack.push(result);

  // writeG
  arg0 = this.stack.pop() || 0;
  this.g = arg0;

  // id
  arg0 = this.stack.pop() || 0;
  result = arg0;
  result = result % 1.0;
  this.stack.push(result);

  // neg
  arg0 = this.stack.pop() || 0;
  result = -arg0;
  result = result % 1.0;
  this.stack.push(result);

  // zero?
  arg0 = this.stack.pop() || 0;
  arg1 = this.stack.pop() || 0;
  arg2 = this.stack.pop() || 0;
  result = arg0 === 0 ? arg1 : arg2;
  result = result % 1.0;
  this.stack.push(result);

  // sin
  arg0 = this.stack.pop() || 0;
  result = Math.sin(arg0);
  result = result % 1.0;
  this.stack.push(result);

  // invsub
  arg0 = this.stack.pop() || 0;
  result = 1 - arg0;
  result = result % 1.0;
  this.stack.push(result);

  // ZERO
  result = 0;
  result = result % 1.0;
  this.stack.push(result);

  // inv
  arg0 = this.stack.pop() || 0;
  result = 1 / arg0;
  result = result % 1.0;
  this.stack.push(result);


  return [
    this.r === undefined ? this.stack.pop() || 0 : this.r,
    this.g === undefined ? this.stack.pop() || 0 : this.g,
    this.b === undefined ? this.stack.pop() || 0 : this.b,
  ];
}

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Okay, enough with register machines. Let’s make something new. This time, a stack based machine!

Rather than keeping it’s memory in a series of memory cells, there will be a single stack of values. All functions can pop values from the top of the stack or push them back on. I will add the ability to read the X/Y value and directly write R/G/B, but you can’t write to the former or read from the latter, so you can’t use them as registers. Let’s see what that looks like!

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Okay. That is slow… Let’s make it faster!

So the main problem we have is that we’re interpreting the code. For every single pixel, for every line of code, we’re doing a few housekeeping things and making at least one function call. For a 400x400 image with just 10 lines of code, that’s 1.6M function calls. Like I said, slow.

So let’s make it faster!

My first idea? Transpile it to Javascript!

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