# Function static parameter names not unique ? parametric type problem

**URL:** <https://discourse.julialang.org/t/function-static-parameter-names-not-unique-parametric-type-problem/3365>\
**Category:** General Usage\
**Created:** [April 25, 2017, 6:03am UTC](https://discourse.julialang.org/t/function-static-parameter-names-not-unique-parametric-type-problem/3365 "2017-04-25T06:03:14Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![purplishrock](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/purplishrock/32/13451_2.png) [@purplishrock](https://discourse.julialang.org/u/purplishrock)\
**Post date:** [April 25, 2017, 6:03am UTC](https://discourse.julialang.org/t/function-static-parameter-names-not-unique-parametric-type-problem/3365/1 "2017-04-25T06:03:14Z")

</div>

error:

ERROR: LoadError: syntax: function static parameter names not unique

I’ve been reading some of the posts about parametric types and inner constructors but I can’t quite seem to get what I’m trying to do to work.

Thanks,

```julia
type Point{T<:Real}
    x :: T
    y :: T
    z :: T
end

function convert{T<:Float64}(::Type{Point{T}}, xyz::Tuple{Float64,Float64,Float64})
    Point(xyz[1], xyz[2], xyz[3])
end

type Plate{T<:Real}
    p0 :: Point{T}
    p1 :: Point{T}
    function Plate{T<:Real}(p0::Point{T}, p1::Point{T})
        if ((p0.x == p1.x) || (p0.y == p1.y) || (p0.z == p1.z))
            new(p0, p1)
        else
            error("Plate definition must have 0 thickness in one dimension")
        end
    end
end

p1 = Plate(Point(3.0,4.0,5.0), Point(3.0, 7.0, 6.0))

```

---

<div class="post-metadata">

**Author:** ![traktofon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/traktofon/32/591_2.png) [@traktofon](https://discourse.julialang.org/u/traktofon)\
**Post date:** [April 25, 2017, 6:54am UTC](https://discourse.julialang.org/t/function-static-parameter-names-not-unique-parametric-type-problem/3365/2 "2017-04-25T06:54:02Z")

</div>

The Julia documentation has [an example](https://docs.julialang.org/en/stable/manual/constructors/#case-study-rational) very similar to your case. It seems like you will need an inner constructor as well as an outer constructor. In detail, in your inner constructor, just write `Plate` instead of `Plate{T<:Real}` (but keep the `Point{T}`s – `T` is still defined from the type parameter), and then add the (seemingly tautological) outer constructor

```julia
Plate{T<:Real}(p0::Point{T}, p1::Point{T}) = Plate{T}(p0,p1)

```

This works for julia 0.5. AFAIK 0.6 has some changes to the inner constructor syntax, maybe there is a way to achieve the same thing without the outer constructor.

---

<div class="post-metadata">

**Author:** ![fengyang.wang](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/fengyang.wang/32/104_2.png) [@fengyang.wang](https://discourse.julialang.org/u/fengyang.wang)\
**Post date:** [April 25, 2017, 6:54am UTC](https://discourse.julialang.org/t/function-static-parameter-names-not-unique-parametric-type-problem/3365/3 "2017-04-25T06:54:51Z")

</div>

It’s not your fault: 0.5 inner constructors are a little weird. (They actually implicitly add static type parameters in some situations. That’s why the error message mentions static parameter names not being unique.) Just make this small change and things will work.

```julia
type Point{T<:Real}
    x :: T
    y :: T
    z :: T
end

function convert{T<:Float64}(::Type{Point{T}}, xyz::Tuple{Float64,Float64,Float64})
    Point(xyz[1], xyz[2], xyz[3])
end

type Plate{T<:Real}
    p0 :: Point{T}
    p1 :: Point{T}
    function (::Type{Plate}){T<:Real}(p0::Point{T}, p1::Point{T})
        if ((p0.x == p1.x) || (p0.y == p1.y) || (p0.z == p1.z))
            new{T}(p0, p1)
        else
            error("Plate definition must have 0 thickness in one dimension")
        end
    end
end

p1 = Plate(Point(3.0,4.0,5.0), Point(3.0, 7.0, 6.0))

```

On 0.6, the 0.5 inner constructor weirdness is deprecated, and will go away in 1.0. For now, to avoid it, just explicitly write `(::Type{Foo})` to make explicit what type a method is being added to.