MATLAB: Script isn’t running

Question

Hi guys, can someone tell me how can i fix this script. Also, how can i know the it number?

for (b-a>tol)
   if g_x1<g_x2
         a=a
         b=x2
         x2=x1
     elseif g_x1>g_x2
         a=x1
         b=b
         x1=x2
     end
  end
for (b-a)<tol
break

Answer 1

for is used only for iterating a fixed number of times. To loop as long as a condition is true, use while