iterative inversion of density_pTX by regula falsi
function pressure_dTX extends Modelica.Icons.Function; input SI.Density d; input SI.Temperature T; input MassFraction X[nX] "Mass fractions"; input FixedPhase phase = 0 "2 for two-phase, 1 for one-phase, 0 if not known"; input Real[nX_gas + 1] n_g_start = fill(0.5, nX_gas + 1) "start value, all gas in gas phase, all water liquid"; output SI.Pressure p; end pressure_dTX;