From fe0e9f81963f8fc9e0cc75063fa28b9ba9cecee0 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Sat, 5 Jun 2021 16:34:31 +0100
Subject: [PATCH] Add the ability to change the base of a fixnum

---
 agb/src/number.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/agb/src/number.rs b/agb/src/number.rs
index b5fb06a7..812ef05b 100644
--- a/agb/src/number.rs
+++ b/agb/src/number.rs
@@ -6,6 +6,14 @@ use core::{
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]
 pub struct Num<const N: usize>(i32);
 
+fn change_base<const N: usize, const M: usize>(num: Num<N>) -> Num<M> {
+    if N < M {
+        Num(num.0 << (M - N))
+    } else {
+        Num(num.0 >> (N - M))
+    }
+}
+
 impl<const N: usize> From<i32> for Num<N> {
     fn from(value: i32) -> Self {
         Num(value << N)
@@ -166,6 +174,15 @@ fn test_division_by_2_and_15(_gba: &mut super::Gba) {
     }
 }
 
+#[test_case]
+fn test_change_base(_gba: &mut super::Gba) {
+    let two: Num<9> = 2.into();
+    let three: Num<4> = 3.into();
+
+    assert_eq!(two + change_base(three), 5.into());
+    assert_eq!(three + change_base(two), 5.into());
+}
+
 impl<const N: usize> Display for Num<N> {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         let integral = self.0 >> N;