Added lume.weightedchoice()

README.md

@@ -64,6 +64,17 @@ raised.
 lume.randomchoice({true, false}) -- Returns either true or false
 ```
 
+### lume.weightedchoice(t)
+Takes the argument table `t` where the keys are the possible choices and the
+values are the choice's weight. A weight should be 0 or above, the larger the
+weight value the higher the probability of that choice being picked. If the
+table is empty or all the weights are 0 or a weight is below zero an error is
+raised.
+```lua
+lume.weightedchoice({ ["cat"] = 10, ["dog"] = 5, ["frog"] = 0 })
+-- Returns either "cat" or "dog" with "cat" being twice as likely to be chosen.
+```
+
 ### lume.shuffle(t)
 Shuffles the values of array `t` in place, returns the array.
 

lume.lua

@@ -67,6 +67,21 @@ function lume.randomchoice(t)
 end
 
 
+function lume.weightedchoice(t)
+  local sum = 0
+  for k, v in pairs(t) do
+    assert(v >= 0, "weight value less than zero")
+    sum = sum + v
+  end
+  assert(sum ~= 0, "all weights are zero")
+  local rnd = lume.random(sum)
+  for k, v in pairs(t) do
+    if rnd < v then return k end
+    rnd = rnd - v
+  end
+end
+
+
 function lume.shuffle(t)
   for i = 1, #t do
     local r = math.random(#t)