Hi all,

I have this test code:

```
import Base.+
mutable struct Polynomial
data::Dict{Int, Real}
function Polynomial(data::Dict{Int, <:Real})
@assert all(n->n>=0, keys(data))
@assert all(!iszero, values(data))
new(data)
end
Polynomial() = new(Dict())
end
function +(P::Polynomial, Q::Polynomial)
""" P + Q """
R = Polynomial()
pds = keys(P.data)
qds = keys(Q.data)
for n in setdiff(pds, qds)
R.data[n] = P.data[n]
end
for n in setdiff(qds, pds)
R.data[n] = Q.data[n]
end
for n in pds â© qds
if (c = P.data[n] + Q.data[n]) != 0
R.data[n] = c
end
end
R
end
function +=(P::Polynomial, Q::Polynomial)
""" P += Q """
pds = keys(P.data)
qds = keys(Q.data)
for n in setdiff(qds, pds)
P.data[n] = Q.data[n]
end
for n in pds â© qds
if (c = P.data[n] + Q.data[n]) != 0
P.data[n] = c
end
end
end
```

I was trying to overload the += operator, but I had this error instead:

```
ERROR: LoadError: syntax: invalid identifier name "+="
Stacktrace:
[1] include at .\boot.jl:317 [inlined]
[2] include_relative(::Module, ::String) at .\loading.jl:1044
[3] include(::Module, ::String) at .\sysimg.jl:29
[4] exec_options(::Base.JLOptions) at .\client.jl:231
[5] _start() at .\client.jl:425
in expression starting at C:\Users\User\Desktop\Tfach\julia_project\test.jl:36
```

how can I define the += operator ?