Add comments to bitwise matching

1 files changed, 5 insertions, 0 deletions

diff --git a/capset.go b/capset.go
index 3fcc814..ae77571 100644
--- a/capset.go
+++ b/capset.go
@@ -144,11 +144,16 @@ func (d *Deck) hasSetWithLast(tableau []Card) bool {
 	}
 	i := len(tableau) - 1
 	for j := 0; j < i; j++ {
+		// Both same and diff are trying to get 11 for each attribute to indicate a
+		// match.
 		same := ^(tableau[i].attrs ^ tableau[j].attrs)
 		diff := tableau[i].attrs ^ tableau[j].attrs
 		for k := j + 1; k < i; k++ {
+			// same and diff become fully computed. 11 indicates match.
 			sameFinal := same & ^(tableau[i].attrs ^ tableau[k].attrs)
 			diffFinal := diff ^ tableau[k].attrs
+			// Shift and AND so that we have a single bit to indicate success. This is
+			// necessary for the OR to function appropriately.
 			sameSingle := sameFinal & (sameFinal >> 1)
 			diffSingle := diffFinal & (diffFinal >> 1)
 			if (sameSingle|diffSingle)&d.isSetBitMask == d.isSetBitMask {