Former Localite Robert M. GrayAnnouncement has been made of the engagement of Miss Edythe Mab Salinger, daughter of Mrs. Dorothea Tamm Gould of Hastings-on-Hudson, N.Y., and David Salinger of Glenview, 111., to Robert Merwin Gray of Cambridge, Mass., formerly of Westport, and son of Mrs. Raymond Daniell of Ottowa, Canada, and Mallory Merwin Gray of North Tarrytown, N.Y.The bride-elect was graduated summa cum laude from Syracuse University and did graduate work at New York University. She is with MacMillan Company, New York Publishing firm.! Mr. Gray is an alumnus of Cheshire Academy, the Davies School in London, England, and Bard College, Annendale-on-Hudson, N.Y.The wedding will take place Dec. 23 in the Hotel Gotham in New York City.