zeroes: branch instead of heap allocation

src/zeroes.rs

@@ -1,40 +1,96 @@
 //find roots of polynomials
 use crate::integer::Planar64;
 
+pub enum Zeroes{
+	Two([Planar64;2]),
+	One([Planar64;1]),
+	Zero,
+}
+impl Zeroes{
+	pub fn len(&self)->usize{
+		match self{
+			Zeroes::Two(z)=>z.len(),
+			Zeroes::One(z)=>z.len(),
+			Zeroes::Zero=>0,
+		}
+	}
+}
+impl From<[Planar64;0]> for Zeroes{
+	fn from(_value:[Planar64;0])->Self{
+		Zeroes::Zero
+	}
+}
+impl From<[Planar64;1]> for Zeroes{
+	fn from(value:[Planar64;1])->Self{
+		Zeroes::One(value)
+	}
+}
+impl From<[Planar64;2]> for Zeroes{
+	fn from(value:[Planar64;2])->Self{
+		Zeroes::Two(value)
+	}
+}
+pub struct ZeroesIter{
+	zeroes:Zeroes,
+	index:usize,
+}
+impl Iterator for ZeroesIter{
+	type Item=Planar64;
+	fn next(&mut self)->Option<Self::Item>{
+		let ret=match self.zeroes{
+			Zeroes::Two(z)=>z.get(self.index).copied(),
+			Zeroes::One(z)=>z.get(self.index).copied(),
+			Zeroes::Zero=>None,
+		};
+		self.index+=1;
+		ret
+	}
+}
+impl IntoIterator for Zeroes{
+	type Item=Planar64;
+	type IntoIter=ZeroesIter;
+	fn into_iter(self)->Self::IntoIter{
+		ZeroesIter{
+			zeroes:self,
+			index:0,
+		}
+	}
+}
+
 #[inline]
-pub fn zeroes2(a0:Planar64,a1:Planar64,a2:Planar64) -> Vec<Planar64>{
+pub fn zeroes2(a0:Planar64,a1:Planar64,a2:Planar64)->Zeroes{
 	if a2==Planar64::ZERO{
-		return zeroes1(a0, a1);
+		return zeroes1(a0,a1);
 	}
 	let radicand=a1.get() as i128*a1.get() as i128-a2.get() as i128*a0.get() as i128*4;
-	if 0<radicand {
+	if 0<radicand{
 		//start with f64 sqrt
 		//failure case: 2^63 < sqrt(2^127)
 		let planar_radicand=Planar64::raw(unsafe{(radicand as f64).sqrt().to_int_unchecked()});
 		//TODO: one or two newtons
 		//sort roots ascending and avoid taking the difference of large numbers
 		match (Planar64::ZERO<a2,Planar64::ZERO<a1){
-			(true, true )=>vec![(-a1-planar_radicand)/(a2*2),(a0*2)/(-a1-planar_radicand)],
-			(true, false)=>vec![(a0*2)/(-a1+planar_radicand),(-a1+planar_radicand)/(a2*2)],
-			(false,true )=>vec![(a0*2)/(-a1-planar_radicand),(-a1-planar_radicand)/(a2*2)],
-			(false,false)=>vec![(-a1+planar_radicand)/(a2*2),(a0*2)/(-a1+planar_radicand)],
+			(true, true )=>[(-a1-planar_radicand)/(a2*2),(a0*2)/(-a1-planar_radicand)].into(),
+			(true, false)=>[(a0*2)/(-a1+planar_radicand),(-a1+planar_radicand)/(a2*2)].into(),
+			(false,true )=>[(a0*2)/(-a1-planar_radicand),(-a1-planar_radicand)/(a2*2)].into(),
+			(false,false)=>[(-a1+planar_radicand)/(a2*2),(a0*2)/(-a1+planar_radicand)].into(),
 		}
-	} else if radicand==0 {
-		return vec![a1/(a2*-2)];
-	} else {
-		return vec![];
+	}else if radicand==0{
+		return [a1/(a2*-2)].into();
+	}else{
+		return [].into();
 	}
 }
 #[inline]
-pub fn zeroes1(a0:Planar64,a1:Planar64) -> Vec<Planar64> {
+pub fn zeroes1(a0:Planar64,a1:Planar64)->Zeroes{
 	if a1==Planar64::ZERO{
-		return vec![];
+		return [].into();
 	}else{
 		let q=((-a0.get() as i128)<<32)/(a1.get() as i128);
 		if i64::MIN as i128<=q&&q<=i64::MAX as i128{
-			return vec![Planar64::raw(q as i64)];
+			return [Planar64::raw(q as i64)].into();
 		}else{
-			return vec![];
+			return [].into();
 		}
 	}
-}
+}