# Trouble with CDGA's with One Generator

Hi all, I've been using the functions associated with the `GCAlgebra`

class
to compute some minimal models for given cohomology algebras.
It works fine whenever my cohomology algebra has 2 or more generators,
but I can't get it to accept a single generator. I am trying, for example:

```
D.<x> = GradedCommutativeAlgebra(QQ, degrees = (2,))
d = D.differential({x:0,})
D = D.cdg_algebra(d)
I = D.ideal(x^3)
R = D.quotient(I)
```

It always fails on the quotient, the objection is that

```
1324 'homomorphisms of graded commutative '
1325 'algebras have only been implemented '
1326 'when the base rings are the same' "
```

I don't get it, pretty printing all objects shows they are all over the rational field. I did figure out that you need a comma to define a single-element tuple otherwise you get "not iterable" errors, but I think that's solved now. Any ideas?

To contrast, something like this runs fine:

```
D.<x,y> = GradedCommutativeAlgebra(QQ, degrees = (2,2))
d = D.differential({x:0, y:0})
D = D.cdg_algebra(d)
I = D.ideal([x^2-y^2,x*y,x^3,y^3])
R = D.quotient(I)
```

Note: it doesn't help to change `D.ideal(x^3)`

to `D.ideal([x^3])`

or `D.ideal([x^3,])`

...
I thought maybe it expected a tuple. I've also seen examples where things like `ideal(x^3)`

are written, so that shouldn't be an issue.

Thanks, Russ

As a workaround, you can define the quotient first, and then define the differential:

`D.<x> = ...`

and then`C = D.quotient(...)`

and then`d = C.differential(...)`

etc.