# Definition of unary operator inside a module, removes the \`Base\` definition
**URL:** https://discourse.julialang.org/t/definition-of-unary-operator-inside-a-module-removes-the-base-definition/28371
**Category:** New to Julia
**Tags:** question
**Created:** [September 4, 2019, 12:02pm UTC](https://discourse.julialang.org/t/definition-of-unary-operator-inside-a-module-removes-the-base-definition/28371 "2019-09-04T12:02:39Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@MatFi](https://discourse.julialang.org/u/MatFi)
#### Post date: [September 4, 2019, 12:02pm UTC](https://discourse.julialang.org/t/definition-of-unary-operator-inside-a-module-removes-the-base-definition/28371/1 "2019-09-04T12:02:39Z")
i have a module in which a dispatch on `+` is defined
```julia
module DriftDiff
function (+)(l::Layer, r::Layer)
...
end
function b()
1.0+10.0
end
end
```
If i call now the function `b()`
```julia
julia> DriftDiff.b()
ERROR: MethodError: no method matching +(::Float64, ::Float64)
You may have intended to import Base.+
```
How can i make `DriftDiff.b()` work again?
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [September 4, 2019, 12:16pm UTC](https://discourse.julialang.org/t/definition-of-unary-operator-inside-a-module-removes-the-base-definition/28371/2 "2019-09-04T12:16:09Z")
What you did is to define a new function named `+`, which doesn’t remove the `Base` definition but [shadows it](https://en.wikipedia.org/wiki/Variable_shadowing) so that it is not visible as `+` within your module. This is a useful default because it prevents unexpected behaviors if you accidentally give a function the same name as some obscure `Base` function. You can still refer to the `Base` definition via `Base.:+`.
However, as the error message suggests, what you probably _meant_ to do is to _extend_ the `+` function in `Base` with a new method for your `Layer` type, rather than defining an entirely new function called `+`. One way to do this, as the error message suggests, is to explicitly `import` the `+` function before defining your method, via `import Base: +`. More commonly, you can specify that you are extending `Base.+` when you define your method:
```julia
function Base.:+(l::Layer, r::Layer)
...
end
```
(The special “quoted” syntax `Base.:+` is only required when extending operators, in order to disambiguate the syntax from a binary operation `Base .+ (...)`. You wouldn’t need it for adding methods to e.g. `Base.div`)
---
### Author:  [@MatFi](https://discourse.julialang.org/u/MatFi)
#### Post date: [September 4, 2019, 12:23pm UTC](https://discourse.julialang.org/t/definition-of-unary-operator-inside-a-module-removes-the-base-definition/28371/3 "2019-09-04T12:23:18Z")
Excellent thanks
> One way to do this, as the error message suggests, is to explicitly `import` the `+` function before defining your method, via `import Base: +`
This was my problem, because the message says `import Base.+` and this I’ve tried without luck, now I know that it has to be ` Import Base:+`.
Thanks for teaching me !!
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [September 4, 2019, 4:24pm UTC](https://discourse.julialang.org/t/definition-of-unary-operator-inside-a-module-removes-the-base-definition/28371/4 "2019-09-04T16:24:21Z")
> [@MatFi](#):
>
> This was my problem, because the message says `import Base.+` and this I’ve tried without luck, now I know that it has to be `Import Base:+` .
`import Base.+` should work (if you do it in the module before your function definition). However, if you want to qualify the function name itself, you have to quote it with `:` as `Base.:+`.
It seems a little inconsistent, so I filed a PR to fix both the error message and to allow quoting in `import` statements:
>
>
> TLDR: This PR allows quoting in \`import\` statements, e.g. \`import Base.:+\`, simi…lar to other Julia contexts, and uses quoting for \`MethodError\` warnings about shadowed operators.
>
> As was \[noted recently on discourse\](https://discourse.julialang.org/t/definition-of-unary-operator-inside-a-module-removes-the-base-definition/28371), the \`MethodError\` printing currently shows a potentially confusing suggestion when a function shadows a \`Base\` function if it is an operator, and in general the quoting of symbols (e.g. \`Base.+\` vs. \`Base.:+\`) was a bit inconsistent.
>
> For example, if you accidentally shadow \`+\`, it prints \`You may have intended to import Base.+\`, which may be confusing because if you try to define the function as \`Base.+\` Julia will give an error. This PR changes the error message to quote operators.
>
> Unfortunately, while \`function Base.:+(...)\` works, \`import Base.:+\` gave a syntax error, which seems a little inconsistent. So this PR also updates the parser to allow quoted symbols in \`import\` statements. Backwards compatible since it was a syntax error previously.