def vert_function(script, function='<STR_LIT>', strict_face_select=True):
if script.ml_version == '<STR_LIT>':<EOL><INDENT>strict_select = '<STR_LIT>'.join([<EOL>'<STR_LIT>',<EOL>'<STR_LIT>'.format(str(strict_face_select).lower()),<EOL>'<STR_LIT>',<EOL>'<STR_LIT>',<EOL>'<STR_LIT>',<EOL>])<EOL><DEDENT>else:<EOL><INDENT>strict_select = '<STR_LIT>'<EOL><DEDENT>filter_xml = '<STR_LIT>'.join([<EOL>'<STR_LIT>',<EOL>'<STR_LIT>',<EOL>'<STR_LIT>'.format(str(function).replace('<STR_LIT:&>', '<STR_LIT>').replace('<STR_LIT:<>', '<STR_LIT>')),<EOL>'<STR_LIT>',<EOL>'<STR_LIT>',<EOL>'<STR_LIT>',<EOL>strict_select,<EOL>'<STR_LIT>'])<EOL>util.write_filter(script, filter_xml)<EOL>return None<EOL>
Boolean function using muparser lib to perform vertex selection over current mesh.

    See help(mlx.muparser_ref) for muparser reference documentation.

    It's possible to use parenthesis, per-vertex variables and boolean operator:
        (, ), and, or, <, >, =
    It's possible to use the following per-vertex variables in the expression:

    Variables:
        x, y, z (coordinates)
        nx, ny, nz (normal)
        r, g, b, a (color)
        q (quality)
        rad
        vi (vertex index)
        vtu, vtv (texture coordinates)
        ti (texture index)
        vsel (is the vertex selected? 1 yes, 0 no)
        and all custom vertex attributes already defined by user.

    Args:
        script: the FilterScript object or script filename to write
            the filter] to.
        function (str): a boolean function that will be evaluated in order
            to select a subset of vertices. Example: (y > 0) and (ny > 0)
        strict_face_select (bool): if True a face is selected if ALL its
            vertices are selected. If False a face is selected if at least
            one of its vertices is selected. ML v1.3.4BETA only; this is
            ignored in 2016.12. In 2016.12 only vertices are selected.

    Layer stack:
        No impacts

    MeshLab versions:
        2016.12
        1.3.4BETA