isl_test_cpp17-generic.cc: work around std::optional::value issue in older macOS

[isl.git] / test_inputs / faddeev.pwqp

[N] -> { [i, j, k] -> (((4 + 6 * N + 2 * N^2) + (-2 - 2 * N) * j) + ((-2 - N) + j) * k) : j = 1 + i and k = 1 + i and i >= 3 and N <= 100 and i <= N and N >= 10 }