Re: Strange behaviour with Arrays and print?

Perl sees your last line as

print( (@fred."\n") );
[download]

... that is, it first evaluates @fred . "\n" and then prints that result.

. evaluates its operands in scalar context. An array in scalar context evaluates to the number of its elements. Your expression then becomes

print( (scalar(@fred),"\n") );
[download]

... which is

print 10,"\n";
[download]

If you want to print an array, maybe put it in string context first:

print "@fred\n";
[download]

Comment on Re: Strange behaviour with Arrays and print? Select or Download Code

Replies are listed 'Best First'.
Re^2: Strange behaviour with Arrays and print? by CountZero (Bishop) on Jul 12, 2014 at 13:04 UTC
or use `say` instead of `print`, then you don't have to append a `"\n"`. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l] [select]
Re^2: Strange behaviour with Arrays and print? by pingufreak83 (Initiate) on Jul 12, 2014 at 13:20 UTC
Hi, but why is this: `print @fred;` [download] not the same? This prints the elements and not the scalar / count number. Kind regards, pingu	[reply] [d/l]
Re^3: Strange behaviour with Arrays and print? by johngg (Canon) on Jul 12, 2014 at 13:36 UTC
Because print takes a list as an argument so `@fred` is not coerced into scalar context. In your original `print @fred."\n"` the concatenation coerces scalar context, hence the "10" but if you'd used a comma instead of a full stop then that would have been a list and the elements of `@fred` would have been printed. `$ perl -Mstrict -Mwarnings -e ' > my @fred = qw{ one two three }; > print @fred . qq{\n}; > print @fred, qq{\n}; > print qq{@fred\n};' 3 onetwothree one two three` [download] I hope this makes things clearer. Cheers, JohnGG	[reply] [d/l] [select]
Re^4: Strange behaviour with Arrays and print? by pingufreak83 (Initiate) on Jul 12, 2014 at 13:41 UTC
Got it, thank you! :)	[reply]
Re^3: Strange behaviour with Arrays and print? by AnomalousMonk (Archbishop) on Jul 12, 2014 at 13:30 UTC
Because you are then passing the array `@fred` to the function print as an argument list; the array is evaluated in list context and yields its individual elements. Update: E.g.: `c:\@Work\Perl>perl -wMstrict -e "sub foo { print $_[1]; print qq{\n}; ;; my @copy_of_arguments = @_; print $copy_of_arguments[1]; print qq{\n}; } ;; my @ra = qw(one two three); foo(@ra); ;; foo('four', 'five', 'six'); " two two five five` [download] See `@_` in perlvar.	[reply] [d/l] [select]