uni update

src/main.zig

@@ -16,19 +16,16 @@ pub fn main() !void {
     defer rl.closeWindow();
 
     rl.setTargetFPS(60);
-    rl.beginDrawing();
-
-    rl.clearBackground(rl.Color.light_gray);
-
-    plotGraph();
-    drawAxis();
-    try markAxis(allocator);
-    calculateArea();
-
-    rl.endDrawing();
 
     while (!rl.windowShouldClose()) {
         rl.beginDrawing();
+
+        rl.clearBackground(rl.Color.white);
+
+        plotGraph();
+        drawAxis();
+        try markAxis(allocator);
+
         rl.endDrawing();
     }
 }
@@ -142,6 +139,34 @@ fn adjustForGridSystem(input_vector: rl.Vector2) rl.Vector2 {
     return new_vector;
 }
 
-fn calculateArea() void {
-    rl.drawText("Test", SCREENWIDTH - 75, 25, 20, rl.Color.red);
+fn calculateArea(val: f32) !void {
+    var buf: u8[20] = undefined;
+
+    const txt = try std.fmt.bufPrintZ(&buf, "{}", .{val});
+    rl.drawText(txt, SCREENWIDTH - 75, 25, 20, rl.Color.red);
+}
+
+const SimpsonsError = error{
+    InvalidParValue,
+};
+
+fn simpsonsRule(start: f32, end: f32, n: usize) !f32 {
+    if (start > end) return SimpsonsError.InvalidParValue;
+
+    const h = (end - start) / @as(f32, @floatFromInt(n));
+
+    var sum: f32 = getY(start) + getY(end);
+
+    var i: usize = 1;
+
+    // we iterate through amount of subintervals
+    while (i < n) : (i += 1) {
+        // calculate x of the slice we're adding (start + )
+        const x = start + i * h;
+
+        // determine weights 4 for odd, 2 for even
+        sum += if (x % 2 == 0) 2 * getY(x) else 4 * getY(x);
+    }
+
+    return (h / 3.0) * sum;
 }