A sixth of kanji.dict is SKK's okuri-ari entries, keyed by a stem and
the letter of the okurigana that follows it — かk: 書 描 掛 —, and no
reading ever ends in a letter, so かく offered 確 and 各 but never 書く,
and no verb or adjective could be converted at all. Now every split of a
complete reading is tried, longest stem first, with the okurigana put
back: かく adds 書く and 描く after the exact candidates, よむ gives
読む, あかい 赤い, おおきい 大きい, いった 言った, かいた 書いた. A stem
that ends in っ writes it in kana too, so いt and いっt agree.