[mercury-users] read_line and lex (was: Many data elements using Mercury on cygwin?)

Simon Taylor stayl at cs.mu.OZ.AU
Fri Feb 7 09:31:59 AEDT 2003

On 07-Feb-2003, Douglas Auclair <dauclair at msn.com> wrote:
> From: Ralph Becket (rafe at cs.mu.OZ.AU)
> >- many files can be read in their entirety and then processed (you'd  use 
> >read_file_as_string);

Any use of read_file_as_string for files which are not known to
be small adds an unnecessary and easily avoided fixed limit to
your program,

> Okay, but these files are big:  one is 12 meg, another 2 meg, and three 
> others at 1 meg, 1/2 meg and 1/2 meg -- my point in using read_line/3 was 
> to collect only the subset of information I need.  Will the OS (cygwin) and 
> the Mercury runtime be able to handle all that?

Possibly, but the way you are doing it is better.

> >- you should seriously consider using lex in extras: it would make  
> >reading and parsing your file a trivial matter.
> Thanks.  I'll look into lex.  As I write scanners and parsers quite often, 
> this particular task was already trivial for me (each line follows the same 
> format, and each line had at most 15 columns, only 3 of which I care 
> about), but if lex is a time-saver I'll use that instead.  What about the 
> lexer module in the library, does it use lex, or are the two entirely 
> disjoint?

They're disjoint -- library/lexer.m is a hand-coded lexer for
Mercury terms.

> Is there some (additional)documentation for it?  (I don't have 
> extras in front of me, so I only see the lexer docs.)

The documentation is in the extras distribution.

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