From 215dfab8a9280bd88aea6d257efbbb48c2e9de27 Mon Sep 17 00:00:00 2001
From: Quaternions <krakow20@gmail.com>
Date: Mon, 16 Sep 2024 12:07:42 -0700
Subject: [PATCH] write body extrapolation from time ratio using ridiculous
 trait bounds

---
 src/physics.rs | 57 ++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 48 insertions(+), 9 deletions(-)

diff --git a/src/physics.rs b/src/physics.rs
index 798edb1..b833bc2 100644
--- a/src/physics.rs
+++ b/src/physics.rs
@@ -836,6 +836,45 @@ impl Body{
 		let dt=time-self.time;
 		self.velocity+(self.acceleration*dt).map(|elem|elem.divide().fix_1())
 	}
+	pub fn extrapolated_position_ratio_dt<Num,Den,N1,D1,N2,N3,D2,N4,N5,N6,T1>(&self,dt:integer::Ratio<Num,Den>)->Planar64Vec3
+		where
+			// Why?
+			// All of this can be removed with const generics because the type can be specified as
+			// Ratio<Fixed<N,NF>,Fixed<D,DF>>
+			// which is known to implement all the necessary traits
+			Num:Copy,
+			Den:Copy+core::ops::Mul<i64,Output=D1>,
+			D1:Copy,
+			Num:core::ops::Mul<Planar64,Output=N1>,
+			Planar64:core::ops::Mul<D1,Output=N2>,
+			N1:core::ops::Add<N2,Output=N3>,
+			Num:core::ops::Mul<N3,Output=N4>,
+			Den:core::ops::Mul<D1,Output=D2>,
+			D2:Copy,
+			Planar64:core::ops::Mul<D2,Output=N5>,
+			N4:core::ops::Add<N5,Output=N6>,
+			N6:integer::Divide<D2,Output=T1>,
+			T1:integer::Fix<Planar64>,
+	{
+		// a*dt^2/2 + v*dt + p
+		// (a*dt/2+v)*dt+p
+		((self.acceleration.map(|elem|dt*elem/2)+self.velocity).map(|elem|dt.mul_ratio(elem))+self.position)
+		.map(|elem|elem.divide().fix())
+	}
+	pub fn extrapolated_velocity_ratio_dt<Num,Den,N1,N2,N3,T1>(&self,dt:integer::Ratio<Num,Den>)->Planar64Vec3
+		where
+			Num:Copy,
+			Den:Copy,
+			Num:core::ops::Mul<Planar64,Output=N1>,
+			Planar64:core::ops::Mul<Den,Output=N2>,
+			N1:core::ops::Add<N2,Output=N3>,
+			N3:integer::Divide<Den,Output=T1>,
+			T1:integer::Fix<Planar64>,
+	{
+		// a*dt + v
+		(self.acceleration.map(|elem|dt*elem)+self.velocity)
+		.map(|elem|elem.divide().fix())
+	}
 	pub fn advance_time(&mut self,time:Time){
 		self.position=self.extrapolated_position(time);
 		self.velocity=self.extrapolated_velocity(time);
@@ -858,21 +897,21 @@ impl Body{
 		//v+a*t==0
 		//goober code
 		if !self.acceleration.x.is_zero(){
-			let t=Time::from(-(self.velocity.x/self.acceleration.x).divide().fix_1());
-			if t0<t&&t<t1{
-				aabb.grow(self.extrapolated_position(t));
+			let t=-self.velocity.x/self.acceleration.x;
+			if t0.to_ratio().lt_ratio(t)&&t.lt_ratio(t1.to_ratio()){
+				aabb.grow(self.extrapolated_position_ratio_dt(t));
 			}
 		}
 		if !self.acceleration.y.is_zero(){
-			let t=Time::from(-(self.velocity.y/self.acceleration.y).divide().fix_1());
-			if t0<t&&t<t1{
-				aabb.grow(self.extrapolated_position(t));
+			let t=-self.velocity.y/self.acceleration.y;
+			if t0.to_ratio().lt_ratio(t)&&t.lt_ratio(t1.to_ratio()){
+				aabb.grow(self.extrapolated_position_ratio_dt(t));
 			}
 		}
 		if !self.acceleration.z.is_zero(){
-			let t=Time::from(-(self.velocity.z/self.acceleration.z).divide().fix_1());
-			if t0<t&&t<t1{
-				aabb.grow(self.extrapolated_position(t));
+			let t=-self.velocity.z/self.acceleration.z;
+			if t0.to_ratio().lt_ratio(t)&&t.lt_ratio(t1.to_ratio()){
+				aabb.grow(self.extrapolated_position_ratio_dt(t));
 			}
 		}
 	}