Elias Assmann wrote:
> On Tue, Apr 01, 2003 at 10:42:57PM -0800, R. Joseph Newton wrote:
>
> > Neither language is strongly typed, as C, Java, or VB are. Although
> > both are type-sensitive, they still restrict identifiers only by
> > contaiment class.
>
> Could you elaborate on that? What do you mean by "type-sensitive"
They both respond to implicit cues as to data type:
my $var1 = "Hi";
my $var2 = "2";
print $var1 + 1 . "\n";
print $var1 + 1 . "\n";
Print $var1 . ", there.\n";
print $var2 . ", there \n";
in each case above, the language first recognizes that the var is
receiving a string. The it converts the string as called for to any
numerical value it may express. We know that it does not handle numerical
operations in the same way as string operations.
> and
> "restrict identifiers ..."?
In genral-purpose use we declare Perl variables as one of three
containment classes:
$ scalar
@ array
% hash
Perl strictly enforces the difference, although it does allow for
conversions through assignment.
#!perl -w
#!perl -w
use strict;
my $my_var = 2;
my @my_var = (9, 2, 3);
my %my_var = ('4', 5, '3', 6);
print "$my_var\n";
print "\n";
foreach (@my_var) {
print "$_\n";
}
print "\n";
foreach (keys %my_var) {
print "$_: $my_var{$_}\n";
}
print "\n";
YIELDS:
Howdy, podner! E:\d_drive\perlStuff>containment.pl
2
9
2
3
4: 5
3: 6
Call it what one will each my_var knows which containment class it was
declared in. erl will not allow operations that are not appropriate for
the type of containment class being addressed. Although Perl will issue a
warning for implicit casts between numeric and string, it will still allow
them:
my $var3 = "cat";
my $var4 = "dog";
if ($var4 > $var3) {
print "dogs are greater than cats\n";
} else {
print "Mroowwwwrrrrr\n";
}
When the above code is run without warnings, the output is simply:
Mroowwwwrrrrr
OTOH, if you do this
my @my_var2 = (9, 2, 3);
...
$my_var2{'my_key'} = "Beat the system";
without warnings turned on, but using strict:
Global symbol "%my_var2" requires explicit package name at
E:\d_drive\perlStuff\
containment.pl line 17.
Execution of E:\d_drive\perlStuff\containment.pl aborted due to
compilation erro
rs.
Without strict, of course, Perl will let you go ahead and create the new
hash %my_var implicitly.
Hmmmm, you know, the more I play with this, the less I see any quantum
difference between Perl's handling of differences between primitive data
types and its handling of differences between containment types. With
either situation, if it sees a sensible conversion to make, it will make
it.
Joseph
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
