MATLAB: Matlab language to C

matlab coder

Why this functions doesn't work on matlab coder

function [Rs] = Racineb(s)

imax=25;

emax=0.00001;

x=s;

if s<0

 Rs='erreur';
 disp('le paramètre entrée s doit être positif')

end

for i=1:imax

 Rs=x-(x^2-s)/(2*x);
 E=abs((Rs-x)/x);
 x=Rs;
 if E<emax
 break
 end

end

if E>emax

    Rs='erreur';

disp('Le nombre de 25 itération a ete atteint sans avoir trouvé la solution')

end

It is saying that this assignment writes a 'double' value into a 'char' type. The problem is with Rs and x.

How can I resolve this problem? Thank you

Don't convert Rs to a char!

Rs is a double here:

Rs=x-(x^2-s)/(2*x);

Here you convert it to a char.

    Rs='erreur';

Use a different variable instead or set Rs to nan.

Before the "for i" loop use

E = emax;

to initialize to some value. MATLAB is not able to quite notice that your "while" loop will always execute at least once.

Also, take another look at your lines

   Rs=x-(x^2-s)/(2*x);
   E=abs((Rs-x)/x);

Those lines would have difficulty if x is not a scalar. Your code itself does not guarantee it, as you assign

x = s;

but what if the parameter is is not a scalar? It would be more robust if you assigned

s = s(1,1);

before the assignment x = s;

zp = find(x==2,1);
X = (1:length(x))-zp;
stairs(X, x)