Zhāng Dūnrén 張敦仁
Style names Zhònggāo 仲篙 and Gǔyú 古餘. Native of Yángchéng 陽城 (Zézhōu 澤州 prefecture, Shānxī). Born Qiánlóng 19 (1754); died Dàoguāng 14 (1834). CBDB id 80926 confirms the lifedates.
Jìnshì of Qiánlóng 43 (1778); served in successive provincial offices in Jiāngxī, Shǎnxī, and Sìchuān, ultimately as àncháshǐ 按察使 (Provincial Surveillance Commissioner) of Jiāngníngfǔ. After retirement in the early Jiāqìng he settled at Yángzhōu and devoted himself to mathematical-philological work in the circle of 焦循 Jiāo Xún, 李銳 Lǐ Ruì, and 阮元 Ruǎn Yuán.
The leading Jiā-Dào-period scholar of medieval Chinese algebra. His three principal mathematical works:
(1) The Qiúyī suànshù 求一算術 (KR3fc041) in 4 juàn — the systematic QiánJiā exposition of 秦九韶 Qín Jiǔsháo’s Dàyǎn qiúyī shù 大衍求一術 (the Chinese Remainder Theorem), the first thorough Qīng exposition of this fundamental SòngYuán algorithm.
(2) A xìcǎo on the Jígǔ suànjīng (KR3fc006) — detailed-procedure exposition of 王孝通 Wáng Xiàotōng’s cubic-equation classic, presented as the Jígǔ suànjīng xìcǎo 緝古算經細草. Parallel to but independent of 李潢 Lǐ Huáng’s KR3fc005 Jígǔ suànjīng kǎozhù.
(3) The Kāifāng bǔjì 開方補記 — supplementary treatment of equation-solving methods, building on the qiúyī and kāifāng lineage.
Zhāng was also a major classical philologist, with substantial editorial work on the Yílǐ 儀禮 and the Hàn shū 漢書. His mathematical work shares the methodological commitments of the JiāDào qiúyī / kāifāng recovery project: working out in full computational detail the procedures that the SòngYuán algebraists had stated only schematically.