Generation of n_th anonymouse Walsh function

I need Walsh functions for fourier approximation of some test function (let it be sinx on interval from -pi to pi). So I need to find n_th Walsh function as a function of x to use in integral for coefficients. Here is my try (I tried to use haddamar matrices)

function y = wal(x,n)
    N = 2^n;
    H = hadamard(N); 
    id = fix(x*N -1e-9) + 1;
    y = H(N,id);
end

But here is my problem, first of all these functions are not correct. Secondly, they are defined only on (0,1) interval, and I don't know how to generalise in on [-pi,pi]. Thirdly input x is an array, and I need to make anonymous func @(x), but then my id is undefined and function is not working at all