How to use 'goto' statement?

I have the problem in the code segment:

if matchedRulesCount==0
        goto('N')
        return
    else
        goto('N1')
        return
    end
fprintf('Number of rules matched are:%d\n',matchedRulesCount);
%LABEL N    
disp('No rule is fired.');
%LABEL N1  
choice=input('Do yo want to try once more? \n0. For No.\n1. For yes. \n');

I get the following error

??? Undefined function or method 'goto' for input arguments of type 'char'.

Answer 1

[Jan]

if matchedRulesCount==0
  N;
else
  choice = N1;
end
return;

function N
disp('No rule is fired.');

function choice = N1  
choice=input('Do yo want to try once more? \n0. For No.\n1. For yes. \n');

It is a very good idea to avoid goto. It is even not a part of Matlab!

[Rahman]

Thanks Jan Simon. It worked.

[Walter Roberson]

Not quite. N1 should also be invoked after N is. The label N has no goto or return or other flow modification, so after N is done, flow should continue on to N1. After N1 is done (either path), flow would "fall off the end of the script" and would not reach the "return" that are shown in the code after the goto()

[Jan]

Correctly, Walter. I've been confused by the "return" statements in the original code, which cannot be reached. Therefore I assumed, that this is a demo code only to illustrate the question. As answer I demonstrated how to use functions instead of GOTOs. While the codes are not equivalent, they demonstrate the different ideas.

[K Vineeth Reddy]

this is not working in my machine.

"A nested function cannot be defined inside a control statement (if, while, for, switch or try/catch).

Be aware that in addition to this message, other messages might appear in the file. Such as, <control statement> might not be aligned with its matching END and Parse error at END: usage might be invalid MATLAB syntax. When you remove the nested function definition from the control statement, these other messages might disappear"

I am getting error like this.

[Walter Roberson]

Please show your code.

Answer 2

[Ilham Hardy]

There is no

goto

function in matlab.

The only

goto

is a user-defined function (script) http://www.mathworks.ch/matlabcentral/fileexchange/26949-matlab-goto-statement

[Stephen23]

Note that that FEX submission introduces itself with this line: "It goes without saying that this code is mainly just for entertainment purposes, since using goto() is considered lazy programming and is a debugging nightmare."

Beginners who find this page and want to use goto should learn how to use functions or other more robust programming syntaxes. This will make their lives much easier.

[Claudio]

as much as people thinks that "goto" is a beginner statement, it helps keeping down complexity and write cleaner code in certain scenarios, tha lack of it is appalling because it forces much more complex patterns where there is absolutely no need for.

It is as appalling as the lack of a finally in the try catch blocks

[Steven Lord]

tha lack of it is appalling because it forces much more complex patterns where there is absolutely no need for.

What examples of such scenarios do you have in mind? It's possible that there's a more efficient way to do what you're thinking about than the implementation you've thought of.

Just in my personal opinion:

Are there cases where having a goto statement in MATLAB could make certain operations easier? Likely, yes. But not, IMO, to the point of being "appalling". To my mind "appalling" is a pretty high bar and not having a feature that has been so hotly debated over multiple decades doesn't clear that bar.

Are there cases where code would be much, much more complicated if MATLAB had a goto statement? Likely, yes. Search MATLAB Answers for "eval" if you want to see how people can make things much more complicated by using a tool when it may not be necessary.

Does the benefit of introducing a goto statement in MATLAB outweight the potential cost (to MathWorks, to design / implement / test / document that statement, and to users who may misuse it to write convoluted code)? That's much less clear. [And no, "just do what other language X does" is not a design for the feature. MATLAB is not C. MATLAB is not C++. MATLAB is not Java, Fortran, Python, or any other language.]

It is as appalling as the lack of a finally in the try catch blocks

That seems like a reasonable enhancement request you could send to Technical Support directly using this link.

Answer 3

[Shruthi rajagopalan]

Hi, Can anyone please help me out with the below query: I want to use a goto statement inside if-else statement.How should i do that? I came across in mathworks that there is no goto in matlab.Only Continue and break is available for For loop and while loop alone. How should i jump to another statement when I am using If-Else Statement? Thanks! Shruthi

[Walter Roberson]

Could you demonstrate the structure you would use to write it in "goto" form?

[Howard Lam]

for i = 1 : N
    statements;
    for j = 1 : M
        statements;
        if x > y
            goto here;
        end
    end
    statements;
    here:
end

I have something like this. Can you help please?

[Kenneth Lamury]

According to user-defined function (script) http://www.mathworks.ch/matlabcentral/fileexchange/26949-matlab-goto-statement, you might be using it wrong. Try the following:

for i = 1 : N
    statements;
    for j = 1 : M
        statements;
        if x > y
            goto(here);
            return %must have a return after the goto function
        end
    end
    statements;
    % LABEL here
end

Remember that it's goto('pointer','file') usage; 'file' is optional.

[Walter Roberson]

Without using the user contributed fake goto, you would use

for i = 1 : N
    statements;
    goto_here = false;
    for j = 1 : M
        statements;
        if x > y
            goto_here = true;
            break;
        end
    end
    if ~goto_here
      statements;
    end
    %here:
end