A question on input and output arguments in a function, interesting.

Hello fellows users of MATLAB. Let me state my question, I really appreciate your attention. I am programming the code of a program which represents a distillation column with controllers. As part of the global iterative process I need to stablish some functions which calculate Entalphies, Liquid Flowrates, Temperatures and Vapor compositions. My problem is that I have a function that needs as input argument a Temperature value(TBUBLE) and the expresion in the function also calculates a temperature value because the program needs it, this is an output value (TBUBLE). In your experience: Is it possible to declare a function with a name for an input argument exactly the same as the name for an output argument?, as in my case TBUBLE.

Thank you .

function [TBUBLE,YBUBLE]=BUBPT(XS,PEP,AVPP,BVPP,TBUBLE)

*

XSS=XS(1:5);
%PEPP=PEP
AVPPP=AVPP(1:5);
BVPPP=BVPP(1:5);

%      LAZO=0.0;
%  Initial values

      SUMYTA=0.0;    
      FSLOPEE=0.0;    

while LAZO <=50

      for K=1:5
  %TBUBLE IS NEEDED AS INPUT ARGUMENT

      PSS(K)=exp(BVPPP(K)+AVPPP(K)/(TBUBLE+460.));
      YBUBLE(K)=PSS(K)*XSS(K)/PEP;     

      SUMYTA=SUMYTA+YBUBLE(K);

      end

      if abs((SUMYTA-1.)<=0.00001)

       %  disp('TEMP-LAZO')

          break

      else

      FEE=SUMYTA*PEP-PEP;

      TSQQ=(TBUBLE+460.)^2;   

      end

      for K=1:5

      FSLOPEE=FSLOPEE-AVPPP(K)*XSS(K)*PSS(K)/TSQQ;

      end
   %TBUBLE is calculated again    
      TBUBLE=TBUBLE-FEE/FSLOPEE;

    % Increase counting

      LAZO=LAZO+1;

      disp('TEMP-LAZO') 

end   

end

[Jan]

abs((SUMYTA-1.) <= 0.00001) does most likely not, what you are expecting: the ABS() is applied after the <= comparison. But the operation abs(true) or abs(false) is not really useful. Do you mean:

abs(SUMYTA-1.) <= 0.00001

[Pepe Vázquez]

Jan Simon, Actually, what you said is true, I didn´t notice that, thank you.

Answer 1

[Walter Roberson]

Yes, it is valid to have an output argument name that is the same as an input argument name. Indeed, there are some internal optimizations that can only occur in this situation.

[Pepe Vázquez]

Ok, Thank you I appreciate your answer.

Answer 2

[Matt Fig]

Even a one-line function is possible in MATLAB. This is a valid function...

function num = myecho(num)

[Pepe Vázquez]

Ok, Thank you I appreciate your answer.