Problem with list ...

[p5pRT]

Migrated from rt.perl.org#5538 (status was 'resolved')

Searchable as RT5538$

[p5pRT]

From u99103@cs.unipune.ernet.in

I want to break a long string in "file" to give me "file2" as output.
For this, I tried following code​:

### Start
open(fd,"file");
open(fd2,">file2");
@​array = <fd>;
$i = 0;
for ($i*70; $i < @​array/70; @​i++)
{
  @​temp = @​array[$i..$i+70];
  print fd2 "@​temp";
}
### End

To my surprise simply

print "@​array[1..10]";
OR
print "$array[1..10]";

were giving me the whole file NOT only 10 characters.

Whether I am doing wrong or a BUG in perl?

Perl Info

Flags:
    category=core
    severity=medium

Site configuration information for perl v5.6.0:

Configured by root at Thu Apr 27 15:49:46 PDT 2000.

Summary of my perl5 (revision 5.0 version 6 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.2.14, archname=i386-linux
    uname='linux zap 2.2.14 #20 fri feb 25 19:44:02 pst 2000 i686 unknown '
    config_args='-de -Dprefix=/usr -Darchname=i386-linux -Dprivlib=/usr/lib/perl5 -Darchlib=/usr/lib/perl5/i386-linux -Dsitelib=/usr/lib/perl5/site_perl -Dsitearch=/usr/lib/perl5/site_perl/i386-linux'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=undef d_sfio=undef uselargefiles=define 
    use64bitint=undef use64bitall=undef uselongdouble=undef usesocks=undef
  Compiler:
    cc='cc', optimize='-O2', gccversion=egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
    cppflags='-fno-strict-aliasing -I/usr/local/include'
    ccflags ='-fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    stdchar='char', d_stdstdio=define, usevfork=false
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lndbm -lgdbm -ldb -ldl -lm -lc -lposix -lcrypt
    libc=/lib/libc-2.1.2.so, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    


@INC for perl v5.6.0:
    /usr/lib/perl5/i386-linux
    /usr/lib/perl5
    /usr/lib/perl5/site_perl/i386-linux
    /usr/lib/perl5/site_perl
    /usr/lib/perl5/site_perl
    .


Environment for perl v5.6.0:
    HOME=/home/stu/b-99/u99103
    LANG (unset)
    LANGUAGE (unset)
    LC_ALL=POSIX
    LD_LIBRARY_PATH=/lib:/usr/lib:/usr/local/lib:/usr/local/oracle/OraHome1/lib
    LOGDIR (unset)
    PATH=/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/usr/openwin/bin:/usr/games:.:/opt/kde/bin:/usr/share/texmf/bin:/usr/local/jdk1.2.2/bin:/usr/local/saclib2.1/bin:/usr/local/oracle/OraHome1/bin:/home/stu/subjects/IP/1999/:/usr/bin:/usr/local/bin:/usr/local/gnu/bin:.:/usr/local/games/bin:/home/stu/b-99/u99103/Misc/mybin:/usr/bin/X11
    PERL_BADLANG (unset)
    SHELL=/sbin/bash

[p5pRT]

From [Unknown Contact. See original ticket]

On 28 Jan 01, at 19​:53, u99103@​cs.unipune.ernet.in wrote​:

I want to break a long string in "file" to give me "file2" as output.
For this, I tried following code​:

### Start
open(fd,"file");
open(fd2,">file2");
@​array = <fd>;
$i = 0;
for ($i*70; $i < @​array/70; @​i++)
{
@​temp = @​array[$i..$i+70];
print fd2 "@​temp";
}
### End

To my surprise simply

print "@​array[1..10]";
OR
print "$array[1..10]";

were giving me the whole file NOT only 10 characters.

Whether I am doing wrong or a BUG in perl?

You appear to be misunderstanding some things about Perl.

I'll go through your code​:

### Start
open(fd,"file");
open(fd2,">file2");
@​array = <fd>;

This reads in the contents of "file", putting each line into a separate
array element of @​array. Lines will still contain their endings
(probably "\n").

$i = 0;

Sets $i to 0.

for ($i*70; $i < @​array/70; @​i++)

This does not compile for me at all. It gives me the warning "Can't
modify array deref in postincrement at -e line 1, near "@​i++"". Is this
really the code you used?

It calculates $i * 70 (which is 0 * 70 = 0, since you just set $i to 0)
and throws this result away. Then it continues while $i is less than
the number of lines in your file, divided by 70 (for example, if your
file had 50 lines, this would be true for $i == 0 but not for $i == 1).
So this is an infinite loop since you're not modifying $i anywhere.

{
@​temp = @​array[$i..$i+70];

This assigns elements from $i to $i+70 to @​temp. If $i is 0, then @​temp
receives the first 71 lines from file, from $array[0] to $array[70]. If
$i is 0, then @​temp receives $array[1] to $array[71].

print fd2 "@​temp";

And this prints the lines in @​temp to file "file2" separated by $",
which is usually a space. The result will be that all lines after the
first will begin with a space.

}
### End

To my surprise simply

print "@​array[1..10]";

This prints array elements from 1 to 10 (10 elements total), separated
by $" (usually a space).

OR
print "$array[1..10]";

Since "1..10" is in scalar context here, it's the "flip-flop" operator,
not the "range" operator, which is almost certainly not what you want
here. (`perldoc perlop`, section "Range Operators", for more
information on the flip-flop and range operators, which are both
spelled ".." (or "...").)

were giving me the whole file NOT only 10 characters.

If you read from the file with @​array = <fd>, then each element of
@​array is one line -- *not* one character. So @​array[1..10] gives you
the second to eleventh lines of the file.

If you want to have characters, you probably want something like
"substr" (or possibly "split //"). See `perldoc -f substr` and `perldoc
-f split` for more information on these functions.

If you can describe in more detail what it is exactly you are trying to
do, the answer can be more specific. However, I suggest you ask the
question on the newsgroup comp.lang.perl.misc, not with perlbug or to
perl5porters.

Cheers,
Philip