compare anonymous function handles
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The following comparison of two function handles should return true in my opinion
f1=@(x,y)(x*y)
f2=@(x,y)(x*y)
isequal(f1,f2)
However, R2016a returns false on this comparison, which is a bug in my opinion. According to the documentation:
Unlike handles to named functions, function handles that represent the same anonymous function are not equal. They are considered unequal because MATLAB cannot guarantee that the frozen values of nonargument variables are the same
In my example, both x and y ARE argument variables. The result is always the same for given arguments. What do you think?
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回答 (2 件)
Matt J
2016 年 4 月 18 日
編集済み: Matt J
2016 年 4 月 18 日
The documentation that you quoted is referring to situations like this:
>> a=1; f1=@(x,y)(x*y+a);
>> a=2; f2=@(x,y)(x*y+a);
These display the same,
>> f1,f2
f1 =
@(x,y)(x*y+a)
f2 =
@(x,y)(x*y+a)
but give different output for the same input arguments:
>> f1(0,0), f2(0,0)
ans =
1
ans =
2
If you consider 2 anonymous functions to be equal if they display the same, you could compare them this way,
>> strcmp(func2str(f1),func2str(f2))
ans =
1
Walter Roberson
2016 年 4 月 18 日
funinfo(1) = functions(f1);
funinfo(2) = functions(f2);
strcmp(funinfo(1).function, funinfo(2).function) && isequal(funinfo(1).workspace{1}, funinfo(2).workspace{1})
3 件のコメント
Walter Roberson
2016 年 4 月 22 日
I doubt Mathworks will change this behaviour any time soon. The alternative would require that Mathworks search all existing function handles, in all scopes, to see if it could find a match.
I suggest you grab a File Exchange Contribution such as http://www.mathworks.com/matlabcentral/fileexchange/34565-micro-cache--memoize-cache-function-results and create a routine that takes in strings and return function handles -- we know that you can convert to string since you do not use any variables from your workspace. The routine would keep a copy of each function handle it generates and upon being presented with the same string would return the same function handle, which would then permit isequal() to operate.
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