Welcome!

River programming language is a homebrew programming language designed as an exercise to understand and build a working programming language and compiler.

As a basic upfront disclaimer this language is not designed to be used in any serious or production sense. It does not explicitly solve any issues that existing languages didn't solve decades ago.

Still, it has been a fun project to flex my programming muscles and dive into the world of languages and compilers.

I have published a web based IDE for you to experiment with the language on your own.

All of the source code for the IDE is included in this repository as well.

Example programs

Calculate pi via Leibniz summation

= sum 0;
= max_iter 10000000;

for = n 0 ,  < n max_iter , = n + n 1
	= sum + sum * 4 / ^ -1 n . + * n 2 . 1
	print sum

kill
Output: 3.14159

Mandelbrot Set

= resolution_x 100
= resolution_y 100

= re_start -2
= re_end 1
= im_start -1
= im_end 1

= max_iteration 100

= re_step / - re_end re_start . resolution_x
= im_step / - im_end im_start . resolution_y


imagebuffer resolution_x resolution_y

for = x_pixel 0 , < x_pixel resolution_x  , = x_pixel + x_pixel 1

	= x_coord + re_start * re_step x_pixel

	for = y_pixel 0 , < y_pixel resolution_y  , = y_pixel + y_pixel 1
		setpixel x_pixel y_pixel 0
		= y_coord + im_start * im_step y_pixel
		= plot 0
		= x 0
		= y 0

		for = iteration 0 , < iteration max_iteration , = iteration + iteration 1
			= xtemp + - * x x . * y y . . x_coord
			= y + * * 2 x . y . y_coord
			= x xtemp
		if > * 2 2 . + * x x . * y y
			setpixel x_pixel y_pixel 1


render
kill

Output:

Programming Guide

1. Declaring variables

   = [variable name] [value]

   Example:

   = pi 3.14159
   print pi
   
   output: 3.14159
   

2. Ternary operators

   [operator] [variable 1] [variable 2] [flag name]

If statements

Legal operators: != == <= < >= >`

Example:

   = counter 0
   = max_count 10
   flag my_flag (( We can jump to this point from anywhere in the code. ))
   + 1 counter counter
   print counter
   > counter max_count my_flag
   kill

Output: 1 2 3 4 5 6 7 8 9 10

3. Mathematical operations

Operations take the form

[operator] [variable 1] [variable 2] [destination variable]

Legal operators: ^ - + * /

Example:

  = a 5;
  = b 7;
  = c 0;
  = d + a b (( this is analogous to a + b = d ))
  = e + a - b c . .  (( this is analogous to a + ( b - c ) = e))
  
  print d
  print e
  
  Output: 12 12

4. for loops

For loops work similarly to C++, in the sense that they have an initializer, a check, and an incremental (which is actually more of a callback)

Consult the following example:

= iter 3
for = a 0 , < a iter , = a + a 1
	print a
	for = b 0 , < b iter , = b + b 1
		print b
kill
Output: 0 0 1 2 3 1 0 1 2 3 2 1 2 3

An important thing to keep in mind when doing for loops is that the compiler only recognizes tabs, NOT SPACES as valid indentations.

5. If statements

if [conditional]
   ... this code runs if conditional is met
... continue from here

Example

if > 5 4
	print 1
	if > 4 5
		print 2
	if < 2 + 2 3
		print 3
	print 4
kill

Output:

1
3
4

If statements do not include else or elif operators. If you need to do an else you could run the inverse of the if statement immediately afterwards.

6. Bitmap graphics

To do bitmap graphics you must create an imagebuffer first.

imagebuffer [x_dim] [y_dim]

then you can set a pixel as either on or off:

setpixel [x_pixel] [y_pixel] [1 or 0]

Finally to output to a file run render. It will be outputted as a random bitmap file and the interpreter will specify the filepath.

Example:

= resolution_x 100
= resolution_y 100

= re_start -2
= re_end 1
= im_start -1
= im_end 1

= max_iteration 100

= re_step / - re_end re_start . resolution_x
= im_step / - im_end im_start . resolution_y


imagebuffer resolution_x resolution_y

for = x_pixel 0 , < x_pixel resolution_x  , = x_pixel + x_pixel 1

	= x_coord + re_start * re_step x_pixel

	for = y_pixel 0 , < y_pixel resolution_y  , = y_pixel + y_pixel 1
		setpixel x_pixel y_pixel 0
		= y_coord + im_start * im_step y_pixel
		= plot 0
		= x 0
		= y 0

		for = iteration 0 , < iteration max_iteration , = iteration + iteration 1
			= xtemp + - * x x . * y y . . x_coord
			= y + * * 2 x . y . y_coord
			= x xtemp
		if > * 2 2 . + * x x . * y y
			setpixel x_pixel y_pixel 1


render
kill

Output:

2. Flags and GOTO

   TODO: There are a lot of bugs with this. I need to add some validation checks related to this.

   flag [flag name]

   Flags serve as reference points that your code can jump to at any point.

   Example:

   = a 5 . 
   = my_flag flag;
   = a + 5 a . .
   print a
   goto my_flag
   
   output: 10 20 40 80 160 ... ...