Noob question: Is all this typecasting normal?

J Kenneth King james at agentultra.com
Tue Jan 6 21:04:04 CET 2009


"Gabriel Genellina" <gagsl-py2 at yahoo.com.ar> writes:

> 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.

I still occassion upon the chance to write some Perl, and even as a
full-time developer who works with Python for a living, I relish every
opportunity.

The funny thing is that I've never had the problem of writing code like
this in Perl. The example is a very poor use-case and doesn't reflect on
the useful/useless-ness of the language itself but more on the choices
of the implementor.

Perl is a very useful language overall and when used properly, very
powerful.



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