we dont need to mask if we're going to shift anyway

nibble.c

@@ -54,7 +54,7 @@ uint64_t bcd_to_64(bcd x) {
 
   for (i = 0; i < 10; ++i) {
     res *= 100;
-    res += ((x.internal[i] & 0xf0) >> 4) * 10;
+    res += (x.internal[i] >> 4) * 10;
     res += (x.internal[i] & 0xf);
   }
 
@@ -68,7 +68,7 @@ char* bcd_to_string(bcd x) {
   char* res = malloc(n+1);
 
   for (i = 0; i < n; i+=2, to++) {
-    res[i]   = ((x.internal[to] & 0xf0) >> 4) + '0';
+    res[i]   = (x.internal[to] >> 4) + '0';
     res[i+1] = (x.internal[to] & 0xf) + '0';
   }