Roger Kwok Wah Hui (December 29 1953 – October 16, 2021) was a computer scientist who worked on array programming languages. He codeveloped the programming language J. Education and career Hui was born in Hong Kong in 1953. In 1966, he immigrated to Canada with his entire family. In 1973, Hui entered the University of Alberta. In his second year he took a course on probability and statistics in which students were expected to learn the programming language APL with little or no formal instruction. He used all the time he could muster on a heavily burdened computer, and benefited from the APL\360 User's Manual (the book APL Language was not published until March 1975). Because the manual was written by Adin Falkoff and Kenneth E. Iverson, Hui thought it reasonable to say he learned APL from Falkoff and Iverson. As a summer student in 1975 and 1976, Hui worked at I. P. Sharp Associates (IPSA) in Calgary, on workspaces for statistical and probability calculations. The major attraction of the job was the unrestricted computer time with access to APL. After receiving a BSc degree with first class honors in computer science in 1977, Hui worked for two years as a full-time programmer and analyst in the new Edmonton office of IPSA, where his main duty was to support clients in their use of APL time-sharing. He attended the APL79 conference in Rochester, New York, where Iverson gave two papers: "The Role of Operators in APL" and "The Derivative Operator". On the way, Hui stopped at IPSA in Toronto and obtained a copy of "Operators and Functions" [IBM Research Report No. 7091, 1978]. He has been studying that paper and its successors ever since. In September 1979, Hui entered the Department of Computer Science at the University of Toronto, and received his MSc in May 1981 with a thesis on "The complexity of some decompositions in matrix algebra." After completing his master's degree, Hui worked from 1981 to 1985 as an APL systems analyst and programmer for the Alberta Energy Company in Edmonton. In February 1982 Hui purchased A Source Book in APL (1981), in which the most memorable papers were "The Design of APL" (1973), "The Evolution of APL" (1978), and "Notation as a Tool of Thought" (1980). Hui's work was described at the APL85 conference in a paper, "DESIGN: A Financial Modelling System", written jointly with his supervisor,