文件列表:

lemon_study (0, 2007-12-01)
lemon_study\lemon (0, 2007-12-01)
lemon_study\lemon\lemon.dsw (533, 2007-12-01)
lemon_study\lemon\lemon.ncb (82944, 2007-12-01)
lemon_study\lemon\lemon.c (133713, 2004-09-06)
lemon_study\lemon\lemon.plg (244, 2007-12-01)
lemon_study\lemon\lempar.c (22530, 2004-09-06)
lemon_study\lemon\lemon.opt (48640, 2007-12-01)
lemon_study\lemon\lemon.dsp (4490, 2007-12-01)
lemon_study\bin (0, 2007-12-01)
lemon_study\bin\lempar.c (22530, 2004-09-06)
lemon_study\bin\example1.y (1817, 2004-09-06)
lemon_study\bin\study.bat (610, 2007-12-01)
lemon_study\bin\example2.y (2713, 2004-09-06)
lemon_study\bin\example3.y (2642, 2004-09-06)
lemon_study\bin\example4.y (1895, 2004-09-06)
lemon_study\bin\lemon.ilk (277352, 2007-12-01)
lemon_study\bin\lemon.exe (274485, 2007-12-01)
lemon_study\example1 (0, 2007-12-01)
lemon_study\example1\example1.cpp (26019, 2007-12-01)
lemon_study\example1\example1.h (215, 2007-12-01)
lemon_study\example1\example1.dsw (539, 2007-12-01)
lemon_study\example1\example1.ncb (33792, 2007-12-01)
lemon_study\example1\exampl1.cpp (748, 2007-12-01)
lemon_study\example1\example1.plg (1500, 2007-12-01)
lemon_study\example1\example1.opt (48640, 2007-12-01)
lemon_study\example1\example1.dsp (4307, 2007-12-01)
lemon_study\example2 (0, 2007-12-01)
lemon_study\example2\exampl2.cpp (660, 2007-12-01)
lemon_study\example2\example2.dsw (539, 2007-12-01)
lemon_study\example2\example2.ncb (33792, 2007-12-01)
lemon_study\example2\example2.cpp (26901, 2007-12-01)
lemon_study\example2\example2.h (215, 2007-12-01)
lemon_study\example2\example2.plg (1596, 2007-12-01)
lemon_study\example2\ex2def.h (68, 2007-12-01)
lemon_study\example2\example2.opt (48640, 2007-12-01)
lemon_study\example2\example2.dsp (4307, 2007-12-01)
lemon_study\example3 (0, 2007-12-01)
lemon_study\example3\example3.dsw (539, 2007-12-01)
lemon_study\example3\example3.ncb (33792, 2007-12-01)
... ...

Copyright (GPL) 2004 mmc mchirico@users.sourceforge.net or mchirico@comcast.net Last Updated: Fri Sep 3 10:18:58 EDT 2004 The latest version of these documents can be downloaded from: http://prdownloads.sourceforge.net/souptonuts/lemon_examples.tar.gz?download To get emailed when there are update and additions: http://sourceforge.net/project/filemodule_monitor.php?filemodule_id=124528 example1.y This is a very simple calulator. To compile the example do the following: $ make Then, to run the example issue the following command: $ ./ex1 OK, what is happening: Take a look at the file "main_part", then, take a look at "example1.c" This main_part is appended to the raw form of example1.c in the Makefile. lemon does not create a complete program - only the necessary subroutines. So it is necessary to build in the main part of a program. If you make your own changes to this example, you should make the changes to example1.y or main_part. example1.c is a generated file, and will be over written every time lemon is run. Disecting main_part: If you take a look at the documentation at the following link: http://www.hwaci.com/sw/lemon/lemon.html You'll see that these are the essential functions that must be called. Note, this is a stripped down simple version with no error checking or tokenizer. The tokens are hardwired in so we can see exactly how lemon operates. void* pParser = ParseAlloc (malloc); The next 4 lines parse the command 15 DIVIDE 5. Parse (pParser, INTEGER, 15); Parse (pParser, DIVIDE, 0); Parse (pParser, INTEGER, 5); Parse (pParser, 0, 0); INTEGER and DIVIDE are assigned values in the generated file example1.h to be the following; #define PLUS 1 #define MINUS 2 #define DIVIDE 3 #define TIMES 4 #define INTEGER 5 Again, this is a generated file, so if any additions are made to this file, they'll be over-written when re-running lemon. example2.y This example is more interesting. A custom token is created in ex2def.h with the following 4 lines: struct Token { const char *z; int value; unsigned n; }; This structure supports both a value and a count. You could add many more values, and allocate memory to z if you wanted. One, note, you cannot put in C++ strings or other STL containers directly into this structure; instead, you would need to have pointers to such structures. Note, if memory was allocated for z, you'd have to free it. example3.y This shows the behavior of a destructor Parse (pParser, 0, t1); ^--^------ only t1 will destruct, since it is called with zero here. example4.y This is the first example that ends the grammer with a newline. In the file example4.y take a look at the following: main ::= in. in ::= . in ::= in state NEWLINE. In main_part4 the last statement here can cause the output to print. Whereas in examples 1-3 it had to end with " Parse (pParser, 0, t0)"; Parse (pParser, ID, t0); Parse (pParser, PLUS, t0); Parse (pParser, ID, t1); Parse (pParser, NEWLINE, t1); example5.y This example puts everything together with flex. But, take a peek at how lexer.l is complied in the Makefile with "flex lexer.l" instead of "flex++ lexer.l". The main_part5 for this example is in C++, so it's necessary to add the extern "C" directives. True it could have been compiled with flex++; but, many people prefer flex for the speed of C in complex projects. This example is run interactively, so entering something like 3+5 is demonstrated below: $ ./ex5 3+5 yylex() 6 yylval.dval 3 yylex() 1 yylval.dval 3 yylex() 6 yylval.dval 5 yylex() 5 yylval.dval 5 In token_destructor t.value= 3 In token_destructor t.n= 0 Result.value=8 Result.n=4 desktop_calc.cc This is an example of a C++ calculator that has not been written with a parser. REFERENCES: (1) Complete source for all examples including the lemon parser generator http://prdownloads.sourceforge.net/souptonuts/lemon_examples.tar.gz?download (2) Example desktop calculator from scratch http://souptonuts.sourceforge.net/code/desktop_calc.cc.html] (3) Example of flex and bison parser http://prdownloads.sourceforge.net/souptonuts/flex_bison.tar.gz?download (3) Home of the lemon parser generator http://www.hwaci.com/sw/lemon/ (4) Home of sqlite http://www.sqlite.org/ (5) Glossory of paser terms http://www.parsifalsoft.com/gloss.html (6) Good introduction to parsers http://www.parsifalsoft.com/isdp.html (7) GNU flex manual http://www.gnu.org/software/flex/manual/ (8) GNU bison manual http://www.gnu.org/software/bison/manual/ (9) The spirit parser September 2003, C/C++ Users Journal Powerful parsing made easy via modern template techniques. Joel de Guzman and Dan Nuffer. http://spirit.sourceforge.net/ (10) Getting a C++ Bison parser to use a C Flex lexer http://www.iunknown.com/000123.html

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