jchen@pollux.usc.edu (Joseph S. Chen) (01/30/88)
Hi,
Does anyone have or know how to get a copy of Fortran-77 lexical
definition in regular expression form and syntatic definition in BNF?
It's fine if the specifications are not "lex" and "yacc" compatible.
Thanks in advance.
Joe Chen
Phone (213) 743-2957
University Computing Services, University of Southern California
UUCP: {sdcrdcf, uscvax}!usc-oberon!joec
ARPA: joec@oberon.usc.edu, jchen@pollux.usc.edu, joec@cse.usc.edupcm@iwarpo3.intel.com (Phil C. Miller) (02/03/88)
In article <6592@oberon.USC.EDU> jchen@pollux.usc.edu (Joseph S. Chen) writes: > Does anyone have or know how to get a copy of Fortran-77 lexical >definition in regular expression form and syntatic definition in BNF? >It's fine if the specifications are not "lex" and "yacc" compatible. >Thanks in advance. Unfortunately, Fortran is a bit too convoluted for lexing with regular expression-based lexers (this point is actually mentioned in the document describing Lex). The problem is that determining whether a token, say "DO", is a keyword or a variable depends on the surrounding context. Therefore, a regular expression cannot capture the essential information about a token. Additionally, since Fortran ignores blanks, it is sometimes difficult to determine whether a token has ended. For example, DO 10 i = 1, 100 is equivalent to DO10i=1,100 It is not possible to determine whether "DO" is a keyword or a variable until the comma is scanned (the fifth following token). As a result, lexical analyzers for Fortran have to be "hand-rolled". Phil Miller {...}!tektronix!omepd!omepd!iwarp!pcm My employer is not responsible for my opinions.