Multiple conditions inside WHILE LOOP

I try to write code to do Bisection method after get input from user, but I'm stuck right now. Basically, after the WHILE statement, I put multiple conditions in order but matlab doesn't work. This is my code:

if true
  % code
c2=input('what is the coefficient for x^2');
c1=input('what is the coefficient for x');
c0=input('What is the last coefficient');
a=input('What is value for a');
b=input('what is value for b');
c=0.5*(a+b);
value=c2*(c^2)+c1*c+c0
while value>=1e-6
    (a>0 && c>0) || (a<0 && c<0);
        a==c
   else b==c

end

I stuck at the WHILE LOOP. I want after I get the "value", matlab will check "value">=1e-6. If that's true, it will set a=c if a and c same sign, otherwise it will set b=c. Then run the equation: value=c2*(c^2)+c1*c+c0 again with update a or b depend on condition until the "value"<1e-6.

Thanks

Answer 1

[Walter Roberson]

a==c is a comparison, not an assignment.

while value>=1e-6
  (a>0 && c>0) || (a<0 && c<0);

means to test whether value>=1e-6 . If it is then the value

 (a>0 && c>0) || (a<0 && c<0)

is computed and then the value is thrown away because of the ';'.

Then you have an "else" even though you are not inside an "if".