bresenham_line.c

/// Bresenham's algorithm in simplistic C
void drawline(int const x0, int const y0, int const x1, int const y1) {
	int const dx = x1 - x0;
	int const dy = y1 - y0;
	int p = 2 * dy - dx;
	for( int x = x0, y = y0; x < x1; x++ ) {
		if( p >= 0 ) {
			putpixel(x, y, 7);
			y++;
			p += 2 * dy - 2 * dx;
		} else {
			putpixel(x, y, 7);
			p += 2 * dy;
		}
	}
}

Struct Version.

struct Vec2 { int x,y; };
void drawline(struct Vec2 const origin1, struct Vec2 const origin2) {
	struct Vec2 const d = { origin2.x - origin1.x, origin2.y - origin1.y };
	int p = 2 * d.y - d.x;
	for( int x = origin1.x, y = origin1.y; x < origin2.x; x++ ) {
		if( p >= 0 ) {
			putpixel(x, y, 7);
			y++;
			p += 2 * d.y - 2 * d.x;
		} else {
			putpixel(x, y, 7);
			p += 2 * d.y;
		}
	}
}

Golang version:

func drawline(x0, y0, x1, y1 int) {
	dx, dy := x1 - x0, y1 - y0
	p, y := 2 * dy - dx, y0
	for x := x0; x < x1; x++ {
		if p >= 0 {
			putpixel(x, y, 7)
			y++
			p += 2 * dy - 2 * dx
		} else {
			putpixel(x, y, 7)
			p += 2 * dy
		}
	}
}