def _param(number, length):
    """Generates ARB assembly for the named vertex/fragment program parameter.
    """

    if length == 1:
        return 'program.local[{}]'.format(number)
    else:
        bits = ['program.local[{}]'.format(n) for n in range(number,
                                                             number + length)]

        return '{{ {} }}'.format(', '.join(bits))