Error: Function definition not supported in this context. Create functions in code file.

function xc = bisect(f,a,b,tol)
if sign(f(a))*sign(f(b)) >= 0,
  error('f(a)f(b)<0 not satisfied!') %ceases execution
end
fa=f(a);
fb=f(b);
k = 0;
while (b-a)/2>tol
  c=(a+b)/2;
  fc=f(c);
  if fc == 0              %c is a solution, done
    break
  end
  if sign(fc)*sign(fa)<0  %a and c make the new interval
    b=c;fb=fc;
  else                    %c and b make the new interval
    a=c;fa=fc;
  end
end
xc=(a+b)/2;  

Answer 1

[Walter Roberson]

you need to store that code in a file named bisect.m

It is not possible to define this kind of function at the MATLAB command line.

[MILAN Barot]

Could you please elaborate

[Walter Roberson]

The error you got "Function definition not supported in this context" is caused by one of two things:

1) In R2016a or earlier, you tried to define a function inside a script -- that is, you had at least one executable line that is not inside any function before the function definition. Defining functions inside scripts is permitted in R2016b and later, and if you had made a mistake in defining a function inside a script in R2016b or later you would have received different error messages; or

2) You tried to define a function at the MATLAB command line, or inside code that you eval() or evalc(). For example,

>> function xc = bisect(f,a,b,tol)
 function xc = bisect(f,a,b,tol)
 ↑
Error: Function definition not supported in this context. Create functions in code file.

It is not permitted to define a function at the MATLAB command line. Instead you need to give the command

edit ./bisect

and paste the code you show into the editor session that comes up, and save the file as bisect.m . Or instead of the "edit" command, you can use the toolbar New -> Script menu entries.