Search is one of the must-have functionalities in Gelman. Here is an SearchQuerySet based upon MySQL full text search extension. It is really cool and neat, but

• first, I don’t want to build my application against specific database extension, even though MySQL is universally picked up in the Web application.
• second, I still prefer more flexible and powerful search syntax other than what MySQL provides
• Last but not the least, I may still need Lucene or Xapian to index, search the PDF, CHM eBooks

So I home-brew the search using PLY, the Python Lex Yacc toolchain. You could check the code here, most of parser.py is just boilerplate, the interesting part is to build django.db.models.Q:

The semantics is quite straightforward: AND(the default), OR operations are supported directly from Q; and only field title is searched. We may extend the syntax using author: like Google does later, so stay tune.

I don’t touch the flex/yacc since the final exam of the class, until today I have to cope with the FORTRAN 90 input data. The input file is like:

with various data formats, flexible lengths of white space, scattered white lines. I first tired the standard string search/match, and soon lost the patience for tedious if..else. Therefore, I decided to try Lex, the very first flex in action.

First, the flex rule. We just need the float pointer number, and ignore all the spaces, new-lines and end-of-file. We expect the token is returned one by one, so we return the flag as soon as the pattern matches.

In main.c, we would like to override default input file handle stdin for yyin if additional argument is fed ( for some reason, this cause the wordpress 503 error, so take a look at the tarball, sorry for the inconveniece). Then we fetch the token one by one, convert the matched yytext to float-point number until the end of file.

At then end, Makefile glues all the parts together.

Here is the tarball for the source code and example input file.