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#Lexer generator algorithm how to
#Lexer generator algorithm code
#Lexer generator algorithm windows

wc is my own implementation of wc that uses a state machine and has an 8-way unrolled inner loop, just included as a sort of speed-of-light comparison.

handcoded is a hand-coded table-driven lexical analyzer that I'll describe below this includes computing a hash value for identifiers (but not looking up in a table), converting float literals to floats, integer literals of different bases to integer numbers, and copying strings character constants to a buffer, converting backslash-escapes (all entries other than "handcoded" do not include any of these operations).

stb_lex (w/symbol hashing) adds to the above looking up a symbol in a symbol (hash) table, just to give some idea of some of the missing time elsewhere none of the other entries include this, although "handcoded" does include the hash function.

however, unlike the flex & handcoded implementations, the stb_lex implementation does not correctly track the file line-count inside /*.*/ comments, so it is not actually usable as is

stb_lex is a lex/flex-alike found in stb.h that builds the tables at runtime, rather than offline, thus avoiding the 'generates source code' problem.

#Lexer generator algorithm how to

flex is the standard flex that was available in 2006 I attempted as best I knew how to make it efficient (note this doesn't parse numeric character constants, nor do the other lexers).

#Lexer generator algorithm code

Runtime performance lexing ~7,500,000 lines of C code using MSVC 6 in 2006: I'm not the only one who reacts this way for example lcc uses a recursiveīut the proof is in the pudding: what if we can just do faster than flex,Īnd the speed of lexing matters? Here's the results I got in 2006 when I did this work Strings with backslash-escaped elements). Is twitchy (shift-reduce conflicts, error handling, etc.) the regularĮxpressions in lex/flex can get annoying (e.g.

#Lexer generator algorithm windows

on Windows where developers don't have them available by default) yacc I've generally found the use of parser generators like lex & yacc toīe painful they generate source code, which complicates the build process Some Strategies For Fast Lexical Analysis when Parsing Programming Languages Sean Barrett, Ībstract: Some techniques I've used to make lexical analysis faster: enhancing state machine traversals with additional inner-loop operations to minimize branch mispredictions, and restricting location-tracking-for-diagnostics to only file byte-offsets.Ĭontextual questions 1. Some Strategies For Fast Lexical Analysis when Parsing Programming Languages UNFINISHED PAPER But I wanted to get it out there sooner rather than later