An error-correcting parse algorithm

ABSTRACT

During the past few years, research into so-called “Syntax Directed Compiler” and “Compiler Compiler” techniques [1, 2, 3, 4, 5, 6] has given hope that constructing computer programs for translating formal languages may not be as formidable a task as it once was. However, the glow of the researchers' glee has obscured to a certain extent some very perplexing problems in constructing practical translators for common programming languages. The automatic parsing algorithms indeed simplify compiler construction but contribute little to the production of “optimized” machine code, for example. An equally perplexing problem for many of these parsing algorithms has been what to do about syntactically incorrect object strings. It is common knowledge that most of the ALGOL or FORTRAN “programs” which a compiler sees are syntactically incorrect. All of the parsing algorithms detect the existence of such errors. Many have considerable difficulty pinpointing the location of the error, printing out diagnostic information, and recovering enough to move on to other correct parts of the object string. It is the author's opinion that those algorithms which do the best job of error recovery are those which are restricted to simpler forms of formal languages.

REFERENCES

• 1: Edgar T. Irons, A syntax directed compiler for ALGOL 60, Communications of the ACM, v.4 n.1, p.51-55, Jan. 1961 [doi>10.1145/366062.366083]
• 2: ---- Towards more versatile mechanical translators. To be published.
• 3: ---- The structure and use of the syntax directed compiler. Ann. Rev. in Autom. Programming, 3, 207-228.
• 4: PAUL,, M. A General Processor for Certain Formal Languages. Symbol Languages in Data Processing. Gordon and Breach, London 1962, 65-74.
• 5: EICKEL, J., PAUL, M., BAUER, F. L., SAMUELSON, K. A syntax controlled generator of formal language processor. Institut ffir Angew. Mat. der Univ. Mainz. Sept., 1962.
• 6: BROOKER, R. A., MACCALLUM, I., MORRIS, D., ROHL, J. S. The compiler compiler. Ann. Rev. Autom. Programming 3, 229-271.
• 7: BACKUS, J. W. The syntax and semantics of the proposed international algebraic language of the Zurich ACM-GAMM Conf. Proc. Intemat. Conf. Inform. Process., UNESCO, (June 1959), 125-132.
• 8: Peter Naur , J. W. Backus , F. L. Bauer , J. Green , C. Katz , J. McCarthy , A. J. Perlis , H. Rutishauser , K. Samelson , B. Vauquois , J. H. Wegstein , A. van Wijngaarden , M. Woodger, Report on the algorithmic language ALGOL 60, Communications of the ACM, v.3 n.5, p.299-314, May 1960 [doi>10.1145/367236.367262]