1 files changed, 18 insertions, 8 deletions
diff --git a/lib/pure/math.nim b/lib/pure/math.nim
index aa64933fb..a9e9010f6 100644
--- a/lib/pure/math.nim
+++ b/lib/pure/math.nim
@@ -85,7 +85,7 @@ proc fac*(n: int): int {.noSideEffect.} =
 proc isPowerOfTwo*(x: int): bool {.noSideEffect.} =
   ## returns true, if `x` is a power of two, false otherwise.
   ## Zero and negative numbers are not a power of two.
-  return (x != 0) and ((x and (x - 1)) == 0)
+  return (x > 0) and ((x and (x - 1)) == 0)
 
 proc nextPowerOfTwo*(x: int): int {.noSideEffect.} =
   ## returns `x` rounded up to the nearest power of two.
@@ -114,18 +114,23 @@ proc sum*[T](x: openArray[T]): T {.noSideEffect.} =
   ## If `x` is empty, 0 is returned.
   for i in items(x): result = result + i
 
-proc mean*(x: openArray[float]): float {.noSideEffect.} = 
-  ## computes the mean of the elements in `x`. 
+template toFloat(f: float): float = f
+
+proc mean*[T](x: openArray[T]): float {.noSideEffect.} =
+  ## computes the mean of the elements in `x`, which are first converted to floats.
   ## If `x` is empty, NaN is returned.
-  result = sum(x) / toFloat(len(x))
+  ## ``toFloat(x: T): float`` must be defined.
+  for i in items(x): result = result + toFloat(i)
+  result = result / toFloat(len(x))
 
-proc variance*(x: openArray[float]): 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 0 .. high(x):
-    var diff = x[i] - m
+  for i in items(x):
+    var diff = toFloat(i) - m
     result = result + diff*diff
   result = result / toFloat(len(x))
 
@@ -347,6 +352,9 @@ proc `^`*[T](x, y: T): T =
 
 proc gcd*[T](x, y: T): T =
   ## Computes the greatest common divisor of ``x`` and ``y``.
+  ## Note that for floats, the result cannot always be interpreted as
+  ## "greatest decimal `z` such that ``z*N == x and z*M == y``
+  ## where N and M are positive integers."
   var (x,y) = (x,y)
   while y != 0:
     x = x mod y
@@ -372,7 +380,9 @@ when isMainModule and not defined(JS):
   randomize(seed)
   for i in 0..SIZE-1:
     assert buf[i] == random(high(int)), "non deterministic random seeding"
-  echo "random values equal after reseeding"
+
+  when not defined(testing):
+    echo "random values equal after reseeding"
 
   # Check for no side effect annotation
   proc mySqrt(num: float): float {.noSideEffect.} =