def find_maxima(x):
    """Find local maxima of x.

    Input arguments:
    x -- 1D list of real numbers

    Output:
    idx -- list of indices of the local maxima in x
    """
    idx = []
    # catch the case when input is an empty list
    if x == []:
        return idx
    
    # catch the case where a maximum is at the edge
    if len(x) > 1:
        if x[0] > x[1]:
            idx.append(0)
        if x[-1] > x[-2]:
            idx.append(len(x)-1)

    # if we only have two values, we are done
    if len(x) == 2:
        return idx

    # other wise for everything not on the edge:
    for i in range(1, len(x)-1):
        if (x[i] > x[i-1]) & (x[i] > x[i+1]):
            idx.append(i)
    
    return sorted(idx)