The apparatus generator has a number of options for filtering out insignificant variants, by ignoring punctuation marks as well as commonplace differences in orthography. All filters are turned on by default.

The punctuation filters are relatively straightforward; when, for example, the daṇḍa filter is turned on, all daṇḍas will be ignored during the comparison of the texts.

In order to filter out orthographic variants, regular expressions are used to normalize the text. Some of these filters may overlap; if a portion of text matches more than one filter, only one filter is applied. Filters are applied in the order that they appear.

Some regular expressions may coincide with sandhi rules described in the Aṣṭādhyāyī, although, in practice, they may not reproduce the sandhi rules exactly.

Examples are given to show how the text is normalized; counterexamples are exceptions which are not normalized.

Normalized spellings may not represent what is generally considered to be “correct” Sanskrit; however, they do reflect orthographic practices as attested in manuscripts.

/(?<=[rṛṙi]|pa)tt|tt(?=[rvy]\S)/t/

• replaces -tt(h)- after consonantal/vocalic r, i, and pa with -t-; replaces -tt(h)- preceding r, v, or y within a word with -t-

• examples
  • arttha ⇒ artha
  • saṃskṛtta ⇒ saṃskṛta
  • prākritta ⇒ prākrita
  • tattvam ⇒ tatvam
  • pattram ⇒ patram
• counterexamples
  • atty annam (source: DCS)

/(?<=[rṛṙ]|[rṛ]\s)(]kgcjṭḍṇdnpbmyvl)\1/\1/

• replaces doubled consonants (excluding t) after consonantal/vocalic r with a single consonant (Cf. Aṣṭādhyāyī 8.4.46)

• examples
  • arddha ⇒ ardha
  • dharmma ⇒ dharma
  • pṛcchati ⇒ pṛchati

/([jtṭd])\1(?=h)/\1/

• replaces -jjh-, -tth-, -ṭṭh-, and -ddh- with -jh-, -th-, -ṭh-, and -dh- respectively (Cf. Aṣṭādhyāyī 8.4.47)

• examples
  • attha ⇒ atha
  • daddhi ⇒ dadhi

/(?:ṃ[lśs]|nn)(?!\S)/n/

• replaces -ṃl, -ṃś, -ṃs, and -nn with -n (Cf. Aṣṭādhyāyī 8.3.7, etc.)

• examples
  • gacchaṃs tu ⇒ gacchan tu
  • puruṣānn eva ⇒ puruṣān eva
• counterexamples
  • aṃśa
  • annam

/[mnñṇṅ](?=[pbmdtnṭḍcjkg])/ṃ/

• replaces nasals preceding certain consonants with an anusvāra (this regular expression is the opposite of rule Aṣṭādhyāyī 8.4.58, as to be more efficient)

• examples
  • nandita ⇒ naṃdita
  • yuñjati ⇒ yuṃjati