Noob question: Is all this typecasting normal?

[Gabriel Genellina]

En Mon, 05 Jan 2009 02:03:26 -0200, Roy Smith <roy at panix.com> escribió:


> The other day, I came upon this gem.  It's a bit of perl embedded in a
> Makefile; this makes it even more gnarly because all the $'s get doubled  
> to
> hide them from make:
>
> define absmondir
> $(shell perl -e ' \                                                      
> sub absmon { my $$a = $$_[0]; \                                          
>    if ( $$^O =~ m/cygwin|MSWin32/i ) {                                    
>       $$prefix = `/bin/mount -p|awk "NR==2{print \\\$$1}"`;
> chomp($$prefix); \
>       $$a = ($$_[1]||"$(PWD)") . "/$$a" \
>          unless ( $$a =~ m !^(:?$$prefix|/|[A-Za-z]:)! ); \
>    } else { $$a = ($$_[1]||"$(PWD)") . "/$$a" unless ( $$a =~ m !^/! );  
> } \
>    return unslash(undot(undotdot($$a))); }; \
> sub unslash ($$) { $$_[0] =~ s://+:/:g; $$_[0] =~ s:/$$::;  
> return($$_[0]);
> }; \
> sub undot ($$) { $$_[0]=~s:/\./:/:g; return ($$_[0]); }; \
> sub undotdot ($$) { my $$in = $$_[0]; \
>       return ( $$in =~ s:/[^/.][^/]*/\.\.::g )?undotdot($$in):$$in; }; \
> print absmon("$(1)","$(2)"); \
> ' )                                                                      
> endef
>
> Barf-o-rama.  I know what it's supposed to do, and I still can't figure  
> it out.

Ouch! Me too, when I come to some piece of Perl code I've written some  
years ago, I invariably think "what's all this noise?". Never happens with  
other languages I've used in the past.

-- 
Gabriel Genellina