how to use function handles
显示 更早的评论
Instead of the following, I want to use function handles and move if-statments out of the loop:
for n=1:10
if a==0
A = function2(n,a,b);
else
A = function1(n,a,b,c,d);
end
end
function A = function1(n,a,b,c,d)
A = n+a+b+c+d; % here it can be any expression
end
function A = function2(n,a,b)
A = n*a*b; % here it can be any expression
end
moving if-statement outside of the loop and using handles:
if a==0
func = @function2;
else
func = @function1;
end
and then I can solve my problem in two ways as
for n=1:10
A = func(n,a,b,c,d);
end
function A = function1(n,a,b,c,d)
A = n+a+b+c+d;
end
function A = function2(n,a,b,~,~)
A = n*a*b;
end
or as
for n=1:10
A = func(n,a,b,c,d)
end
function A = function1(n,a,varargin)
b = varargin{1};
c = varargin{2};
d = varargin{3};
A = n+a+b+c+d;
end
function A = function2(n,a,varargin)
b = varargin{1};
A = n*a*b;
end
Is there any more elegant way to do this?
采纳的回答
Yongjian Feng
2021-8-29
You don't need varargin
function A = function1(n,a,b, c, d)
A = n+a+b+c+d;
end
function A = function2(n,a,b, ~, ~)
A = n*a*b;
end
7 个评论
Stephen23
2021-8-30
This is the best approach. In contrast when you use VARARGIN you lose the clarity of this function signature, which:
- shows the variable names in MATLAB Editor (e.g. tab completion / pop-up help)
- clearly indicates which variables are not used within the function
G A
2021-8-30
@G A: using a structure is also good approach. Which approach to use depends on many things, you will have to find the right balance/optimum for your project and needs, e.g.:
structure:
- useful when you have many arrays (e.g. more than 6 or 7) which easily lead to confusion when supplied as positional input arguments (we regularly get questions on this topic).
- might be easier to process when those arrays are optional
input arguments:
- (partially) self-documentating names
- pop-up help in the Editor, etc.
I am sure that other users on this forum can add other benefits or considerations.
G A
2021-8-30
Stephen23
2021-8-30
"what is the main difficulty to make (or reason not to make) it possible in the Editor to higlight structure name with its field throughout a function like it occurs with simple variables when you click on it or select it?"
You have to consider that variables in MATLAB are dynamically typed. In general it is difficult to determine the type of a variable until runtime (e.g. changes to function scoping, variables created dynamically, inputs are not typed, etc.)
G A
2021-8-31
更多回答（1 个）
I think the basic idea you need is
f1 = @(x) x;
f2 = @(x) x.^2;
f = @(a,x) (a~=0)*f1(x) + (a==0)*f2(x);
f(0,2)
f(1,2)
4 个评论
Hm. Not finding a good way to handle this that does not potentially result in empty, Inf, or NaN when one of the functions does not have all the arguments. For example, you could pass zeros into the function when they are not needed, but it is potentially hazardous:
f1 = @(x) x;
f2 = @(x,y) x.^2 + y.^2;
f = @(a,x,y) (a~=0)*f1(x) + (a==0)*f2(x,y);
f(0,2,3)
f(1,2,0)
the cyclist
2021-8-29
Searching keywords such as conditional anonymous function MATLAB turns up a lot of these same ideas. I did not find a great solution.
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