Marshall Ward Lochbaum is an array language programmer and implementer with a background in J and Dyalog APL. He is the designer of I, BQN, and (with dzaima) Singeli. His work on and publications about Dyalog and BQN often deal with high-performance primitive implementations, particularly with vector instructions. He was a panellist on the Array Cast from 2022 to 2025 and has been a significant contributor to the APL Wiki.
Born in Raleigh, North Carolina in 1993, Lochbaum attended Raleigh Charter High School where he was taught J by Henry Rich. He continued programming in J as a hobbyist and in summer jobs at ThomasNet (where he assisted in creating Jsoftware product Jd) and BEST, llc. Lochbaum attended the University of North Carolina at Chapel Hill, graduating with majors in mathematics and computer science in winter 2014 and again with a master’s degree in computer science in 2016. He created the I programming language, incorporating tacit functional and array programming concepts, in 2012.
From February 2017 until June 2020, he worked as a software developer at Dyalog Ltd., mainly on speeding up the implementation of Dyalog APL, but also on language development and the additions of Dyalog APL 18.0 in particular. He frequently hosted workshops and gave presentations at Dyalog user meetings. At this time he developed the Structural Under concept, which although not added to Dyalog was published through Adám Brudzewsky’s Extended Dyalog APL.
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