How to specify function signature for function handles in MATLAB code generation?

Question

I want to compile a MEX from a function that has the following code (MATLAB R2015a):

function r = MyFunc(x,type)
    ind = randi(numel(x), 1);
    getInd = @getIndFixed;
    if strcmpi(type, 'random')
        ind = numel(x);
        getInd = @getIndRandom; % error here
    end
    x(getInd(ind)) = 1;
end
function k = getIndFixed(n)
    k = n;
end
function k = getIndRandom(n)
    k = randi(n, 1);
end

I get the type mismatch error between getIndFixed and getIndRandom at the line specified above:

Type mismatch: function_handle getIndFixed ~= getIndRandom.

Is there a way around this problem?
For instance, a way to specify that both functions have the same signature?

In C, the signature of the function would be:

int (*getInd)(int);
int getIndFixed(int);
int getIndRandom(int);
//...
getInd = getIndFixed;
getInd = getIndRandom;

score 0 · Answer 1 · answered Aug 24 '16 at 16:56

You cannot change function handles to different functions after they are assigned in code generation. Unlike "C" these function calls are resolved at compile time. If your type input is constant then you can write your code as

function r = MyFunc(x,type)
    if strcmpi(type, 'random')
        ind = numel(x);
        getInd = @getIndRandom; % error here
    else
        ind = randi(numel(x), 1);
        getInd = @getIndFixed;
    end
    x(getInd(ind)) = 1;
end

If type is not constant you need to move everything inside if or else branch.

How to specify function signature for function handles in MATLAB code generation?

1 Answers1