  Let C be an algebraically closed field and X a projective curve over C.
Consider an ordinary linear differential equation, or a linear differ- ence
equation, with coefficients in the field of rational functions of X, and assume
that its Galois Group G has finite determinant group and is reductive. In this
context, the ideal of algebraic relations satisfied by a full system of
solutions is generated by the G-invariants it contains. This result extends a
theorem of E. Compoint.
