Have you ever wondered how a compiler works? If so, this project is for you.
This weekend I'll write a compiler that translates a code written in a very simple programming language Wend (short for a week-end) into GNU assembly. This repository, however, will contain more than the final code. It will tell you a story about compilers.
So behold, here is a program that uses virtually all concepts in Wend:
fun main() {
// square root of a fixed-point number
// stored in a 32 bit integer variable, shift is the precision
fun sqrt(n:int, shift:int) : int {
var x:int;
var x_old:int;
var n_one:int;
if n > 65535 { // pay attention to potential overflows
return 2 * sqrt(n / 4, shift);
}
x = shift; // initial guess 1.0, can do better, but oh well
n_one = n * shift; // need to compensate for fixp division
while true {
x_old = x;
x = (x + n_one / x) / 2;
if abs(x - x_old) <= 1 {
return x;
}
}
}
fun abs(x:int) : int {
if x < 0 {
return -x;
} else {
return x;
}
}
// 25735 is approximately equal to pi * 8192;
// expected value of the output is sqrt(pi) * 8192 approx 14519
println sqrt(25735, 8192);
}There will no be dynamic memory allocation, no pointers, no garbage collection. There will be nested functions, function overloading and type checking.
And as usual, there will be a program with a raytracer :)
make runIt is so dull to compute Fibonacci numbers, so here are more eyecandy examples for our compiler, check gfx/*.wend files.
make gfx
