CODEWITHSUNDEEP
octave
Davide
Davide

Reputation: 2124

Run octave script file containing a function definition

I've a very newbie octave question.
Running this code in octave console is working fine:

function fibo = recfibo(n)
  if ( n < 2 )
    fibo = n;
  else
    fibo = recfibo(n-1) + recfibo(n-2);
  endif
endfunction
disp(recfibo(5))

By inserting this code in an external file named for example file.m, and executing it through octave file.m an error occurs:

warning: function name 'recfibo' does not agree with function filename '/Users/admin/Google Drive/file.m' error: 'n' undefined near line 2 column 8 error: called from octave at line 2 column 3

How should I resolve this particular problem?

Upvotes: 11

Views: 16203

Answers (2)

rahnema1
rahnema1

Reputation: 15837

As stated in the answer provided by @CrisLuengo here you have created a function file instead of a script file and they are treated differently in Octave. Because it is a function file Octave executes it by calling the function it defines with no arguments and nargout = 0. So you will get an error that n is undefined.

Another problem is that the function name 'recfibo' does not agree with function filename 'file'. In such cases Octave internally changes the name of the function to the name of the function file so the name is changed to 'file'. Therefor Octave and the function itself will forget the original function name and unfortunately the function cannot call itself recursively!

I like the @CrisLuengo 's answer but I think the more idiomatic and preferable way is always using function files instead of script files, though the script file solution is the only solution that works in previous Octave versions (Octave 3.X).

You can change your code to:

function file
    disp(recfibo(5))
endfunction
function fibo = recfibo(n)
    if ( n < 2 )
        fibo = n;
    else
        fibo = recfibo(n-1) + recfibo(n-2);
    endif
endfunction

Upvotes: 10

Cris Luengo
Cris Luengo

Reputation: 60444

Add 1; as the first line of the file:

1;

function fibo = recfibo(n)
  if ( n < 2 )
    fibo = n;
  else
    fibo = recfibo(n-1) + recfibo(n-2);
  endif
endfunction

disp(recfibo(5))

Any M-file that starts with a function definition is a function M-file, not a script M-file. By adding a meaningless statement to the top, you turn it into a script.

In MATLAB (since fairly recently), a script M-file can define functions at the end of the script. There you'd put the disp line at the top of the file, and have the function block at the end, without any script lines after it. However, Octave requires functions to be defined before you use them, hence it has to come before the script line that uses the function. Octave allowed the definition of functions within a script file before MATLAB introduced that feature, hence their implementation is not compatible with that of MATLAB.

Upvotes: 24

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