From 8ee6204a42e8a6a9c4db3a4f166429961678ea24 Mon Sep 17 00:00:00 2001
From: Quaternions <krakow20@gmail.com>
Date: Mon, 9 Sep 2024 14:45:47 -0700
Subject: [PATCH] invent wide_div + test

---
 fixed_wide/src/fixed.rs | 17 ++++++++++++++---
 fixed_wide/src/tests.rs | 14 ++++++++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/fixed_wide/src/fixed.rs b/fixed_wide/src/fixed.rs
index 4cdfdef..c8b1969 100644
--- a/fixed_wide/src/fixed.rs
+++ b/fixed_wide/src/fixed.rs
@@ -277,7 +277,7 @@ impl_shift_operator!( Fixed, Shr, shr, Self );
 // WIDE MUL: multiply into a wider type
 // let a = I32F32::ONE;
 // let b:I64F64 = a.wide_mul(a);
-macro_rules! impl_wide_mul{
+macro_rules! impl_wide_not_const_generic{
 	(
 		(),
 		($lhs:expr,$rhs:expr)
@@ -286,7 +286,18 @@ macro_rules! impl_wide_mul{
 		{
 			paste::item!{
 				pub fn [<wide_mul_ $lhs _ $rhs>](self,rhs:Fixed<$rhs,{$rhs*32}>)->Fixed<{$lhs+$rhs},{($lhs+$rhs)*32}>{
-					Fixed::from_bits(self.bits.as_::<BInt<{$lhs+$rhs}>>()*rhs.bits.as_::<BInt<{$lhs+$rhs}>>())
+					let lhs=self.bits.as_::<BInt<{$lhs+$rhs}>>();
+					let rhs=rhs.bits.as_::<BInt<{$lhs+$rhs}>>();
+					Fixed::from_bits(lhs*rhs)
+				}
+				/// This operation cannot represent the fraction exactly,
+				/// but it shapes the output to have precision for the
+				/// largest and smallest possible fractions.
+				pub fn [<wide_div_ $lhs _ $rhs>](self,rhs:Fixed<$rhs,{$rhs*32}>)->Fixed<{$lhs+$rhs},{($lhs+$rhs)*32}>{
+					// (lhs/2^LHS_FRAC)/(rhs/2^RHS_FRAC)
+					let lhs=self.bits.as_::<BInt<{$lhs+$rhs}>>().shl($rhs*64);
+					let rhs=rhs.bits.as_::<BInt<{$lhs+$rhs}>>();
+					Fixed::from_bits(lhs/rhs)
 				}
 			}
 		}
@@ -295,7 +306,7 @@ macro_rules! impl_wide_mul{
 
 //const generics sidestepped wahoo
 macro_repeated!(
-	impl_wide_mul,(),
+	impl_wide_not_const_generic,(),
 	(1,1),(2,1),(3,1),(4,1),(5,1),(6,1),(7,1),(8,1),(9,1),(10,1),(11,1),(12,1),(13,1),(14,1),(15,1),
 	(1,2),(2,2),(3,2),(4,2),(5,2),(6,2),(7,2),(8,2),(9,2),(10,2),(11,2),(12,2),(13,2),(14,2),
 	(1,3),(2,3),(3,3),(4,3),(5,3),(6,3),(7,3),(8,3),(9,3),(10,3),(11,3),(12,3),(13,3),
diff --git a/fixed_wide/src/tests.rs b/fixed_wide/src/tests.rs
index 01fb9f1..43fa2ab 100644
--- a/fixed_wide/src/tests.rs
+++ b/fixed_wide/src/tests.rs
@@ -20,6 +20,20 @@ fn test_wide_mul(){
 	assert_eq!(aa,crate::types::I64F64::ONE);
 }
 
+#[test]
+fn test_wide_div(){
+	let a=I32F32::ONE*4;
+	let b=I32F32::ONE*2;
+	let wide_a=a.wide_mul_1_1(I32F32::ONE);
+	let wide_b=b.wide_mul_1_1(I32F32::ONE);
+	let ab=a.wide_div_1_1(b);
+	assert_eq!(ab,crate::types::I64F64::ONE*2);
+	let wab=wide_a.wide_div_2_1(b);
+	assert_eq!(wab,crate::fixed::Fixed::<3,96>::ONE*2);
+	let awb=a.wide_div_1_2(wide_b);
+	assert_eq!(awb,crate::fixed::Fixed::<3,96>::ONE*2);
+}
+
 #[test]
 fn test_wide_mul_repeated() {
 	let a=I32F32::from(2);