Charles Gregory Nelson

Charles Gregory "Greg" Nelson (27 March 1953 – 2 February 2015) was an American computer scientist.

Nelson grew up in Honolulu. As a boy he excelled at gymnastics and tennis. He attended the University Laboratory School. He received his B.A. degree in mathematics from Harvard University in 1976. He received his Ph.D. in computer science from Stanford University in 1980 under the supervision of Robert Tarjan. He lived in Juneau for a year before settling permanently in the San Francisco Bay Area.

His thesis work influenced both program verification and automated theorem proving, especially in the area now known as satisfiability modulo theories, where he contributed techniques for combining decision procedures, as well as efficient decision procedures for quantifier-free constraints in first-order logic and term algebra. He received the Herbrand Award in 2013:

for his pioneering contributions to theorem proving and program verification, such as his seminal work with Derek Oppen on the combination of satisfiability procedures and fast congruence closure algorithms, the development of the highly influential theorem prover Simplify, and his role in the creation of the field of extended static checking.

He was instrumental in the development of the Simplify theorem prover used by ESC/Java. He also made significant contributions in several other areas. He contributed to the area of programming language design as a member of the Modula-3 committee. In distributed systems he contributed to Network Objects. He made pioneering contributions with his constraint-based graphics editors (Juno and Juno-2), window systems (Trestle), optimal code generation (Denali), and multi-threaded programming (Eraser).