I want to do something like:

```
function foo(x::Array{T,1}, y::Array{T,1})
n1 = length(x)
n2 = length(y)
z = zeros(T, n1+n2)
...
end
```

First problem is that I actually need to write

```
function foo(x::Array{T,1} where T, y::Array{T,1} where T)
...
```

But then the subsequent use of T gives me an UndefVarError.