Increase enchantment on weapon randarts.

It was generally agreed that weapon randarts are a bit weaker than non-weapon
randarts on average. This commit buffs them by increasing their accuracy and
damage enchantment by about 3 each on average (while maintaining the same
[-6,+12] range of possibilities).

1 files changed, 13 insertions, 0 deletions

diff --git a/crawl-ref/source/random.cc b/crawl-ref/source/random.cc
index f17e4716b5..669cb7dd0b 100644
--- a/crawl-ref/source/random.cc
+++ b/crawl-ref/source/random.cc
@@ -206,6 +206,19 @@ int random2avg(int max, int rolls)
     return (sum / rolls);
 }
 
+// biased_random2() takes values in the same range [0, max) as random2() but
+// with mean value (max - 1)/(n + 1) biased towards the bottom end.
+// This can be thought of as the smallest of n _distinct_ random integers
+// chosen in [0, max + n - 1).
+// Never use with n < 2.
+int biased_random2(int max, int n)
+{
+    for (int i = 0; i < max; i++)
+        if (x_chance_in_y(n, n + max - 1 - i))
+            return i;
+    return 0;
+}
+
 // originally designed to randomise evasion -
 // values are slightly lowered near (max) and
 // approach an upper limit somewhere near (limit/2)