Merge pull request #1031 from hondew/berry-yield

Document minor berry yield bug

2 files changed, 20 insertions, 3 deletions

diff --git a/include/constants/berry.h b/include/constants/berry.h
index d413b9947..8f1e7cd82 100644
--- a/include/constants/berry.h
+++ b/include/constants/berry.h
@@ -25,4 +25,11 @@
 #define BERRY_STAGE_BERRIES     5
 #define BERRY_STAGE_SPARKLING   255
 
+// Berries can be watered in the following stages:
+// - BERRY_STAGE_PLANTED
+// - BERRY_STAGE_SPROUTED
+// - BERRY_STAGE_TALLER
+// - BERRY_STAGE_FLOWERING
+#define NUM_WATER_STAGES 4
+
 #endif // GUARD_CONSTANTS_BERRY_H
diff --git a/src/berry.c b/src/berry.c
index 7a8ab37fa..fe4a66af6 100644
--- a/src/berry.c
+++ b/src/berry.c
@@ -1200,6 +1200,15 @@ static u8 GetNumStagesWateredByBerryTreeId(u8 id)
     return BerryTreeGetNumStagesWatered(GetBerryTreeInfo(id));
 }
 
+// Berries can be watered at 4 stages of growth. This function is likely meant
+// to divide the berry yield range equally into quartiles. If you watered the
+// tree n times, your yield is a random number in the nth quartile.
+//
+// However, this function actually skews towards higher berry yields, because
+// it rounds `extraYield` to the nearest whole number.
+//
+// See resulting yields: https://gist.github.com/hondew/2a099dbe54aa91414decdbfaa524327d,
+// and bug fix: https://gist.github.com/hondew/0f0164e5b9dadfd72d24f30f2c049a0b.
 static u8 CalcBerryYieldInternal(u16 max, u16 min, u8 water)
 {
     u32 randMin;
@@ -1215,10 +1224,11 @@ static u8 CalcBerryYieldInternal(u16 max, u16 min, u8 water)
         randMax = (max - min) * (water);
         rand = randMin + Random() % (randMax - randMin + 1);
 
-        if ((rand & 3) > 1)
-            extraYield = rand / 4 + 1;
+        // Round upwards
+        if ((rand % NUM_WATER_STAGES) >= NUM_WATER_STAGES / 2)
+            extraYield = rand / NUM_WATER_STAGES + 1;
         else
-            extraYield = rand / 4;
+            extraYield = rand / NUM_WATER_STAGES;
         return extraYield + min;
     }
 }