Also when it is the name of a meter, the irregular form viṣṭara is used.,
By Sutra 3.3.34 the word विष्टार is formed denoting a sort of metre called विष्टारपंक्तिः ॥
Why do we say when denoting 'the name of a chhandas'? Observe पटस्य विस्तारः ॥
In fact this sutra makes unnecessary the sutra 3.3.34. To avoid this difficulty, some say that the sutra 3.3.34 is not confined to the preposition वि, so that we can form प्रस्तारपङ्क्तिः संसारपङ्क्ति ॥,