Abū al-Ḥassan, Aḥmad Ibn Ibrāhīm, al-Uqlīdisī (Arabic: أبو الحسن أحمد بن ابراهيم الإقليدسي, fl. 952) was a Muslim Arab mathematician of the Islamic Golden Age, possibly from Damascus, who wrote the earliest surviving book on the use of decimal fractions with Hindu–Arabic numerals, Kitāb al-Fuṣūl fī al-Ḥisāb al-Hindī (The Book of Chapters on Hindu Arithmetic), in Arabic in 952. The book is well preserved in a single 12th-century manuscript, but other than the author's name, original year of publication (341 AH, 952/3 AD) and the place (Damascus) we know nothing else about the author: after an extensive survey of extant reference material, mathematical historian Ahmad Salīm Saʿīdān, who discovered the manuscript in 1960, could find no other mention of him. His nickname al-Uqlīdisī ("the Euclidean") was commonly given to people who sold manuscript copies of Euclid's Elements.
In the introductory remarks to his Arithmetic, Al-Uqlīdisī claims that he traveled to confer with every arithmetic expert he knew of, and read every previous book he could find, and comprehensively synthesized this previous work while adding his own ideas.
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