# Zero() and TwicePrecision
**URL:** https://discourse.julialang.org/t/zero-and-twiceprecision/81208
**Category:** New to Julia
**Tags:** question, bug
**Created:** [May 17, 2022, 3:55pm UTC](https://discourse.julialang.org/t/zero-and-twiceprecision/81208 "2022-05-17T15:55:07Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@denshd](https://discourse.julialang.org/u/denshd)
#### Post date: [May 17, 2022, 3:55pm UTC](https://discourse.julialang.org/t/zero-and-twiceprecision/81208/1 "2022-05-17T15:55:07Z")
Hello! I’ve recently found a weird behaviour of `StepLenRange`. Consider:
```julia
N = 10
faces = range(start=0, stop=1, length=(N + 1))
cells = range(start=(0 + faces.step), step=faces.step, length=N)
```
On my computer (`julia v.1.7.2`) it produces the following error:
```julia
ERROR: MethodError: no method matching zero(::Base.TwicePrecision{Float64})
Stacktrace:
[1] _rangestyle(#unused#::Base.Unordered, #unused#::Base.ArithmeticUnknown, a::Base.TwicePrecision{Float64}, step::Base.TwicePrecision{Float64}, len::Int64)
@ Base .\range.jl:168
[2] range_start_step_length(a::Base.TwicePrecision{Float64}, step::Base.TwicePrecision{Float64}, len::Int64)
```
So, I think the problem with `0 + faces.step`. But is this a bug or a feature?🙂
EDIT:
the following works well:
```julia
x = 0:0.1:1
step = x.step
0 + x.step
```
which produces:
```julia
Base.TwicePrecision{Float64}(0.1, -5.551115123125763e-18)
```
---
### Author:  [@oxinabox](https://discourse.julialang.org/u/oxinabox)
#### Post date: [May 17, 2022, 4:02pm UTC](https://discourse.julialang.org/t/zero-and-twiceprecision/81208/2 "2022-05-17T16:02:46Z")
The fields of `StepLenRange`, like the fields of pretty much all other types in Base, and thoughout the julia ecosystem are not part of the public API for that type.
And the `Base.TwicePrecision` type is intentionally not part of the public API for `Base`.
This works fine if you use the same `step` accessor function.
```julia
julia> N = 10
10
julia> faces = range(start=0, stop=1, length=(N + 1))
0.0:0.1:1.0
julia> cells = range(start=(0 + step(faces)), step=step(faces), length=N)
0.1:0.1:1.0
```
The `Base.TwicePrecision` type is an implementation detail.
It’s intentionally very limitted and doesn’t subtype `Number` because things don’t work with it in general.
---
### Author:  [@denshd](https://discourse.julialang.org/u/denshd)
#### Post date: [May 17, 2022, 4:13pm UTC](https://discourse.julialang.org/t/zero-and-twiceprecision/81208/3 "2022-05-17T16:13:16Z")
Thank you!
I didn’t really know about
> accessor functions
and now I’m reading about
> public API
and how to recognize it 🙂