remove varzm functions

the external abi is to call var,
the internal abi doesn' need to branch to alternative functions based on whether mean is given as zero
that simply made the dispatch less straightforward to understand
even though doing an exact comparison to 0 isn't generally reliable

ref #6273, which initially introduced these functions as the public API, before changing them to be the internal implementation

base/statistics.jl

@@ -76,25 +76,6 @@ function var(iterable; corrected::Bool=true, mean=nothing)
     end
 end
 
-function varzm{T}(A::AbstractArray{T}; corrected::Bool=true)
-    n = length(A)
-    n == 0 && return convert(real(momenttype(T)), NaN)
-    return sumabs2(A) / (n - Int(corrected))
-end
-
-function varzm!{S}(R::AbstractArray{S}, A::AbstractArray; corrected::Bool=true)
-    if isempty(A)
-        fill!(R, convert(S, NaN))
-    else
-        rn = div(length(A), length(r)) - Int(corrected)
-        scale!(sumabs2!(R, A; init=true), convert(S, 1/rn))
-    end
-    return R
-end
-
-varzm{T}(A::AbstractArray{T}, region; corrected::Bool=true) =
-    varzm!(reducedim_initarray(A, region, 0, real(momenttype(T))), A; corrected=corrected)
-
 centralizedabs2fun(m::Number) = x -> abs2(x - m)
 centralize_sumabs2(A::AbstractArray, m::Number) =
     mapreduce(centralizedabs2fun(m), +, A)
@@ -159,20 +140,12 @@ varm{T}(A::AbstractArray{T}, m::AbstractArray, region; corrected::Bool=true) =
     varm!(reducedim_initarray(A, region, 0, real(momenttype(T))), A, m; corrected=corrected)
 
 
-function var{T}(A::AbstractArray{T}; corrected::Bool=true, mean=nothing)
+var{T}(A::AbstractArray{T}; corrected::Bool=true, mean=nothing) =
     convert(real(momenttype(T)),
-            mean == 0 ? varzm(A; corrected=corrected) :
-            mean === nothing ? varm(A, Base.mean(A); corrected=corrected) :
-            isa(mean, Number) ? varm(A, mean::Number; corrected=corrected) :
-            throw(ArgumentError("invalid value of mean, $(mean)::$(typeof(mean))")))::real(momenttype(T))
-end
+            varm(A, mean === nothing ? Base.mean(A) : mean; corrected=corrected))
 
-function var(A::AbstractArray, region; corrected::Bool=true, mean=nothing)
-    mean == 0 ? varzm(A, region; corrected=corrected) :
-    mean === nothing ? varm(A, Base.mean(A, region), region; corrected=corrected) :
-    isa(mean, AbstractArray) ? varm(A, mean::AbstractArray, region; corrected=corrected) :
-    throw(ArgumentError("invalid value of mean, $(mean)::$(typeof(mean))"))
-end
+var(A::AbstractArray, region; corrected::Bool=true, mean=nothing) =
+    varm(A, mean === nothing ? Base.mean(A, region) : mean, region; corrected=corrected)
 
 varm(iterable, m::Number; corrected::Bool=true) =
     var(iterable, corrected=corrected, mean=m)