Not able to use function handles in MATLAB 2006b version.

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Kishor
Kishor 2011-7-29
At the time of debugging function handles are working properly but when run complete program it fails. I am not able to find out cause behind that. Please reply.
Thanks & Regards, Kishor Dongare.

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回答（3 个）

Paulo Silva
Paulo Silva 2011-7-29
Not enough info, from MATLAB 2006b documentation I see that it supports function handles, please provide more details like the error that MATLAB gives and a sample of the code.
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Walter Roberson
Walter Roberson 2011-10-12
Jan does not like to be sent email on such matters.
I do not have 2006b, but I am pretty good at analyzing errors *when I am told what the error is*. "it fails" is not enough description to go on.
Kishor
Kishor 2011-10-12
I had four function
1. Main
2. Handles
3. level1_function
4. level2_function
Function Main and Handles are on same directory.
Function level1_function and level2_function are in different-different directory.
1. Call main function.
definitions of all functions are:
%%%%%%%%%%
%%%%%%%%%% Main function :
function Main()
% Generate handles for function 'level1_function' and 'level2_function'.
Handles();
% Load function handle in current workspace for function
% 'level1_function'.
SUB_GetFuncHandle();
% Call function 'level1_function' using function handle.
level1_function();
end
%% Subfunction :
function SUB_GetFuncHandle()
global function_handle;
assignin('caller','level1_function',function_handle.handles(1));
end
%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%% Handle function
function Handles()
% Change folder structure if neccessary for generating function handle
% Save present directory
Present_Dir = pwd;
% Change directory to function 'level1_function' dir and generate function handle.
cd('E:\Testing\Level1');
function_handle.handles(1) = @level1_function;
% Change directory to function 'level2_function' dir and generate function handle.
cd('E:\Testing\Level2');
function_handle.handles(2) = @level2_function;
% Chage to original dir
cd (Present_Dir);
%% Save handle struct as 'global' in base workspace
evalin('base','global function_handle');
assignin('base','function_handle',function_handle);
end
%%%%%%%%%%
%%%%%%%%%% Function :
function level1_function()
% Load function handle in current workspace for function
% 'level2_function'.
SUB_GetFuncHandle();
level2_function('Wats up??????');
end
%% Sub function :
function SUB_GetFuncHandle()
global function_handle;
assignin('caller','level2_function',function_handle.handles(2));
% Check STACK data for function : level2_function
% Function handle is present for function level2_function
% Two options 1. Step run till the end and
% 2. Press F5
% Check the result.
sprintf(['\n Check MATLAB workspace ''STACK'' data of function : ''level2_function''',...
'\n Function handle is present for function level2_function',...
'\n If then continue....\n Two options 1. Step run till the end or',....
'\n\t\t\t 2. Press F5',...
'\n Check the result.'])
keyboard
end
%%%%%%%%%
%%%%%%%%%Function :
function level2_function( input_args )
sprintf(input_args)
%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%
Error message if Main function called with no break point.
Same function work file in matlab 2010a.
??? Error using ==> level2_function
Too many output arguments.
Error in ==> level1_function at 7
level2_function('Wats up??????');
Error in ==> Main at 6
level1_function();

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Walter Roberson
Walter Roberson 2011-10-12
Do not use plain arrays to store function handles. Use cell arrays. Otherwise, your line
assignin('caller','level1_function',function_handle.handles(1));
invokes the function handle stored in function_handle.handles, passing it an argument of 1, and that is in a context where an output value is expected to satisfy the assignin(). If you were using cell arrays the line would be
assignin('caller','level1_function',function_handle.handles{1});
which would not invoke the function function handle.
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Kishor
Kishor 2011-10-12
Still problem not solved.
My question is why it works fine if I run script step by step and throws error when run the script without breakpoint.

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Fangjun Jiang
Fangjun Jiang 2011-10-12
The code runs without error if you fix:
missing global definition in function Handles()
duplicated function SUB_GetFuncHandle()
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Walter Roberson
Walter Roberson 2011-10-12
You have an 'end' statement in your main() routine. The JIT is allowed, in such a case, to assume that no variables will be "poofed into existence". You violate that assumption, so MATLAB is allowed to just not know about the poofed variables, and is allowed to operate corruptly if it encounters such a variable.
Before assigning a variable in a function workspace via assignin() or evalin() or load(), you should initialize the variable. You can initialize to anything at present, but better for potential future optimizations would be if you were to assign something of the same class as it will eventually become.
Kishor
Kishor 2011-10-13
@Fangjun : Thank for your efforts.
I don't know why it is showing error to me even in 7.1 version of MATLAB and run without error in step execution.
@Walter : I didn't get your first comment.Can you elaborate using example.
I have tried with initialization of variables in function workspace before assigning, it's working.
One more thing even if I haven't initialized variable and assigned function handle to function workspace
Now before using function handle, I made operation like
"functions(var);"
and then used the variable as function handle script run without error.

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