# Allow L = 0 in solve

Registered by
Anders Logg

Add check in solve() function (but not in LinearVariation

a = dot(grad(

L = 0

...

solve(a==L, u, bc)

## Blueprint information

- Status:
- Complete

- Approver:
- None

- Priority:
- Low

- Drafter:
- None

- Direction:
- Needs approval

- Assignee:
- None

- Definition:
- Obsolete

- Series goal:
- Accepted for 1.1.x

- Implementation:
- Unknown

- Milestone target:
- None

- Started by

- Completed by
- Garth Wells

### Whiteboard

MSA: This is not solvable in UFL because the zero rhs form is not currently representable in pure UFL, and UFL cannot create a zero valued dolfin Constant. However ufl.Equation does not check the type of its rhs, so dolfin is free to handle this by checking the number of arguments of lhs (1 argument means F == 0, 2 arguments means a == 0).

(?)