The word puraḥ 'in front of', when indeclinable and in composition with a verb, is called gati,
The pronoun पूर्व 'front' with the affix असि forms पुरस्, and by 1.1.38 it becomes an Avyaya. (See 5.3.39 pur being substituted for purva). The object by making it gati is threefold (1) compounding by 2.2.18 (2) accent by 6.2.49 (3) to change the : h into स् by 8.3.40. As पुरस्कृत्य, पुरस्कृतम् and यत् पुरस्करोति, when not an indeclinable we have पूः, पुरौ, पुरः कृत्वा काण्डंगतः.,