Re: Confusing syntax error with grep

Don't try to futz with

grep (expr), @list;
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grep ((expr), @list);
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or any such... you just confuse the hell out of the parser and out of someone trying to read it. Instead use this syntax for grep:

grep { block } @list;
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Those are curly braces setting off a block, not parenthesese setting off an expression. So your code would become:

    grep {
        ( -f "$path/$_" ) and 
        ( $_ =~ m/\.(java|xml|cpp|c|h|inc|pas)$/i ) and
        ( $self->Scan_File( "$path/$_", $out, $target )
    } @files );
    # Also scan any subdirectories.
    grep {
        ( ( -d "$path/$_" ) and 
          ( $_ !~ /^\.+$/ ) and # but avoid . and ..
          ( $self->parseDir( "$path/$_", $out, $target )
        )
    } @files;
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However, it also doesn't make sense because you are using grep in a void context. grep is meant to filter a list (reduce some of the contents out of list1 into list2). If you just want to apply a block of code against every item in a list, think of using map or foreach. Most folks here will complain, likewise, if you use map in a void context (for the same reason, sort of, that I complain about you using grep... the purpose of map (in perl) is to *mutate* a list... although in some other language paradigms one might think of map as making sense in a void context... but that's another argument).

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Re^2: Confusing syntax error with grep by revdiablo (Prior) on Aug 12, 2004 at 16:42 UTC
However, it also doesn't make sense because you are using grep in a void context. Not necessarily. The first grep is in void context, but the last one may or may not be -- it depends on how the subroutine is called. ~~My guess is he took some working code and added a second `grep` at the end, without really realising how it worked.~~ Update: It's pointless to guess how it happened. Kindly ignore that sentence. :-)	[reply] [d/l]
Re^2: Confusing syntax error with grep by gumpu (Friar) on Aug 12, 2004 at 17:25 UTC
"However, it also doesn't make sense because you are using grep in a void context. grep is meant to filter a list (reduce some of the contents out of list1 into list2). If you just want to apply a block of code against every item in a list, think of using map or foreach. Most folks here will complain, likewise, if you use map in a void context" Guess I agree on using map instead of grep. But I find `foreach` ugly. `foreach ( @alist ) { if ( condition( $_ ) ) { do_something( $_ ); } }` [download] Is far less pretty to the eye than: `map { condition( $_ ) and do_something( $_ ) } @alist;` [download] OK, map ( or grep ) has to create a list which is not used. I used to worry about that too. However, given the size of an list in an average problem and the amount of memory that is nowadays present in a computer it is no longer relevant to worry about it. For instance in my case the list holds the names of all files in a single directory. That will be 1 to 1000 elements or so. Compared to the 256 Mbyte that is available in my computer this is peanuts. So I stopped worrying about it and instead worry about making it readable. Of course it would be even nicer if there was a construct in perl like: `{ do_something( $_) } forall ( @alist ) where { condition( $_ ) }` [download] Have Fun	[reply] [d/l] [select]
Re^3: Confusing syntax error with grep by ysth (Canon) on Aug 12, 2004 at 18:48 UTC
Of course it would be even nicer if there was a construct in perl like: `{ do_something( $_) } forall ( @alist ) where { condition( $_ ) }` You mean like: `do_something( $_ ) for grep condition( $_ ), @alist;` ? Update: `condition( $_ ) and do_something( $_ ) for @alist;` is going to be faster because it doesn't have to loop twice.	[reply] [d/l] [select]
Re^4: Confusing syntax error with grep by gumpu (Friar) on Aug 12, 2004 at 19:45 UTC
That comes pretty close yes :) Have Fun	[reply]
Re^3: Confusing syntax error with grep by gumpu (Friar) on Aug 12, 2004 at 18:38 UTC
Come to think of it: `foreach ( @alist ) { if ( condition( $_ ) ) { do_something( $_ ); } }` [download] can be written as `foreach ( @alist ) { condition( $_ ) and do_something( $_ ) }` [download] Which is as pretty as the `map` version. The point about worrying too much about memory still stands though. Have Fun	[reply] [d/l] [select]


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