How to call rootfinder as a function?

[Felipo Soares]

I'm calculating molecular volume using a cubic EoS (peng robinson), so I need to solve the implicit function. I am trying to use pass rootfinder as a function so it can calculate volume/pressure given temperature and pressure/volume as input, but I keep getting the following error:

Wrong number or type of arguments for overloaded function 'Function_call'.
  Possible prototypes are:
    call(self,dict:DM,bool,bool)
    call(self,[DM],bool,bool)
    call(self,[SX],bool,bool)
    call(self,dict:SX,bool,bool)
    call(self,dict:MX,bool,bool)
    call(self,[MX],bool,bool)
  You have: '(Function,([SX],[int|SX]))'

The code follows below

R=8314;
g=9.81;mi=3.64e-3;
rho_l=760;Mg=16.7;
Ta=348;Va=64.34;
y=SX.sym('y',4)

z = SX.sym('x_PR',3)#0 is temperature, 1 is pressure, 2 is volume

Tc_PR=190.6;
Pc_PR=46.04*1.013e5;
w_PR=0.011;

R_PR=8.314;
a_PR=0.45724*(R_PR**2)*Tc_PR**2/Pc_PR;
b_PR=0.07780*R_PR*Tc_PR/Pc_PR;
        
k_PR=0.3764+1.54226*w_PR-0.26992*w_PR**2;

alpha_PR=(1+k_PR*(1-sqrt(z[0]/Tc_PR)))**2;

#p_PR=R_PR.*T./(V_PR-b_PR)-alpha_PR*a_PR./(V_PR.**2+2*b_PR.*V_PR-b_PR.**2);

PengRobinson=z[1]-R_PR*z[0]/(z[2]-b_PR)-alpha_PR*a_PR/(z[2]**2+2*b_PR*z[2]-b_PR**2);


PReosP1=Function("f1", [z[1],vertcat(z[0],z[2])],[PengRobinson])
PReosV1=Function("f2", [z[2],vertcat(z[0],z[1])],[PengRobinson])

PReosP=rootfinder("PReosP",'kinsol' ,PReosP1)
PReosV=rootfinder("PReosV", 'kinsol' ,PReosV1)

#those are some tests to see if it works
print(PReosP([100], [300,0.01]))
print(PReosP([200], [400,0.01]))

print(PReosP1([252064], [300,0.01]))
print(PReosP1([335102], [400,0.01]))
print(PReosV([0.01], [400,335102]))

#%%



#where the error happens
Pat=PReosP([R*Ta*y[0]/(Mg*Va)],[Ta,(Mg*Va)/(y[0]*1000)]);

[Bruno M L]

Hi!

Pat=PReosP([R*Ta*y[0]/(Mg*Va)],[Ta,(Mg*Va)/(y[0]*1000)]);

There is a comma in the second argument. Probably that's it.

Bruno

[Felipo Soares]

Yeah, in my case the second argument is a list with first element the temperature and the second element the molar volume. The first argument of the function is the initial guess. When I pass numerical values like the example below it works fine

print(PReosP([100], [300,0.01]))

[Bruno M L]

Sorry, I got confused.

From the error, it appears that the argument is a mix of 'int'  and 'SX'. Are you sure you want to call the function symbolically with 'y' as a SX?

I cant replicate in matlab right now so I dont know how I ca