deduplicate code in randn

Author: nsajko

src/extras/random.jl

@@ -82,16 +82,15 @@ end
 # normal variates
 
 function randn(rng::AbstractRNG, ::Type{DoubleFloat{T}}) where {T<:IEEEFloat}
-    urand1, urand2 = rand(rng, DoubleFloat{T}, 2)
-    urand1 = urand1 + urand1 - 1
-    urand2 = urand2 + urand2 - 1
-    s = urand1*urand1 + urand2*urand2
+    urand1, urand2, s = ntuple(i -> zero(DoubleFloat{T}), Val{3}())
 
-    while s >= 1 || s === 0
+    while true
         urand1, urand2 = rand(rng, DoubleFloat{T}, 2)
         urand1 = urand1 + urand1 - 1
         urand2 = urand2 + urand2 - 1
         s = urand1*urand1 + urand2*urand2
+
+        (s >= 1 || s === 0) || break
     end
 
     s = sqrt( -log(s) / s )