From 44246b670921aca1d31cb74dcc00139b5ed9a2c2 Mon Sep 17 00:00:00 2001
From: Josep Sanjuas <jsanjuas@gmail.com>
Date: Sat, 18 Apr 2015 13:38:15 +0200
Subject: [PATCH] Document toFloat is necessary

---
 lib/pure/math.nim | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/pure/math.nim b/lib/pure/math.nim
index ef9c69e3cf..05c2cf57cb 100644
--- a/lib/pure/math.nim
+++ b/lib/pure/math.nim
@@ -125,6 +125,7 @@ proc mean*[T](x: openArray[T]): float {.noSideEffect.} =
 proc variance*[T](x: openArray[T]): float {.noSideEffect.} =
   ## computes the variance of the elements in `x`. 
   ## If `x` is empty, NaN is returned.
+  ## ``toFloat(x: T): float`` must be defined.
   result = 0.0
   var m = mean(x)
   for i in items(x):