Interpret a marker and return a result depending on environment.

    :param marker: The marker to interpret.
    :type marker: str
    :param execution_context: The context used for name lookup.
    :type execution_context: mapping

def interpret(marker, execution_context=None):
    """
    Interpret a marker and return a result depending on environment.

    :param marker: The marker to interpret.
    :type marker: str
    :param execution_context: The context used for name lookup.
    :type execution_context: mapping
    """
    try:
        expr, rest = parse_marker(marker)
    except Exception as e:
        raise SyntaxError('Unable to interpret marker syntax: %s: %s' % (marker, e))
    if rest and rest[0] != '#':
        raise SyntaxError('unexpected trailing data in marker: %s: %s' % (marker, rest))
    context = dict(DEFAULT_CONTEXT)
    if execution_context:
        context.update(execution_context)
    return evaluator.evaluate(expr, context)