QuickScan mystery resolved

[Zachary Deretsky]

do {} while (<cond>); is no different than, for
example:

print if (/pattern/);

Been around for a long long time.

-Peter

---
Peter A. Vogel

[Zachary Deretsky]

Thanks, Peter. Actually the "Programming Perl" camel book lists this
under "Universal Blunders" on page 529. I had to discover this myself,
but the problems did not stop there.

Here is the correct version of my scanner:

sub cons::iScan {
    my(@includes);
    ISCAN: while(1) {
         if(/^%(include|import|extern)\s+(\w+\.)(i|ii|iic|iim|hpp)\s*$/) {
             push (@includes, "$2$3");
     };
     last ISCAN if(!($_ = <scan::quickscan::SCAN>));
   }
    close(scan::quickscan::SCAN);
    @includes
};

Two issues are worth noting:

1. Filehandle is not a variable as the authors of "Perl Cookbook" point
out in a cloudy discussion in chapter 7.0. It is best to pass it
in a variable, say $fHandle = *SCAN; The book also mentions that
filehandles live in packages, so one should use complete
scan::quickscan::SCAN.

2. $_ which is implicitly passed as the argument to the (user written)
scanner is not the same as $_ inside this scanner, hence the
assignment in the last if clause.

Here is the relevant cons calling code:

    return () unless open(SCAN, $file->rpath);
    while(<SCAN>) {
        push(@includes, grep($_ ne '', &$code));
    }
    close(SCAN);


To spare other users much suffering I plea to replace it with simple
interface:

@includes = &code($file->rpath);

The user function should open the file, close it and return a list of
include files. What could be more simple? Am I missing something?

Actually, complete solution should associate a scanner with file
extension: if my scanner for .i files returns an .hpp file, then .hpp
scanner should be called for that.

My other issues are still unresolved:

PATH for QuickScan and variables in Depends and Command methods.

Where are you, Steven? SOS!

Thanks, Zach.