
{{alias}}( σ )
    Returns the differential entropy of a half-normal distribution.

    If provided `NaN`, the function returns `NaN`.

    If provided `σ ≤ 0`, the function returns `NaN`.

    Parameters
    ----------
    σ: number
        Scale parameter.

    Returns
    -------
    out: number
        Entropy.

    Examples
    --------
    > var v = {{alias}}( 1.0 )
    ~0.7258
    > v = {{alias}}( 5.0 )
    ~2.3352

    See Also
    --------
