www.developer.com/lang/article.php/2184681
April 10, 2003 Neat and Tidy FormattingThe DBI features a couple of utility functions that can be used to tidy up strings into a form suitable for easy reading. These two functions are For example, to use #!/usr/bin/perl -w # # ch04/util/neat1: Tests out the DBI::neat() utility function. # use DBI; ### Declare some strings to neatify my $str1 = "Alligator's an extremely neat() and tidy person"; my $str2 = "Oh no\nhe's not!"; ### Neatify this first string to a maxlen of 40 print "String: " . DBI::neat( $str1, 40 ) . "\n"; ### Neatify the second string to a default maxlen of 400 print "String: " . DBI::neat( $str2 ) . "\n"; ### Neatify a number print "Number: " . DBI::neat( 42 * 9 ) . "\n"; ### Neatify an undef print "Undef: " . DBI::neat( undef ) . "\n"; exit; which generates the output of: String: 'Alligator's an extremely neat() and...' String: 'Oh no he's not!' Number: 378 Undef: undef demonstrating that string values are quoted,[10] whereas values known to be numeric are not. The first string has been truncated to the desired length with While the
#!/usr/bin/perl -w
#
# ch04/util/neat2: Tests out the DBI::neat_list() utility function
use DBI qw( neat_list );
### Declare some strings to neatify
my @list = ( 'String-a-string-a-string-a-string-a-string',
42, 0, '', undef );
### Neatify the strings into an array
print neat_list( \@list, 40, ", " ), "\n";
exit;
which generates the output of: 'String-a-string-a-string-a-string-a...', 42, 0, '', undef This example also shows that the utility functions can be imported into your package so you can drop the DBI uses Numeric TestingThe final utility function supplied by DBI that we'll look at is quite a curious one called
This may seem rather a curious thing to want to do, but in the case of handling large quantities of data, it's useful for working out which values might need to have their quotes escaped via the The returned array will contain the same number of values as the original data array, with the elements containing one of three values signifying the following: true The original value is a number. false The original value is not a number. undef The original value is empty or undefined. The following example illustrates how this process works:
#!/usr/bin/perl -w
#
# ch04/util/lookslike1: Tests out the DBI::looks_like_number()
function.
#
use DBI;
### Declare a list of values
my @values = ( 333, 'Choronzon', 'Tim', undef, 'Alligator',
1234.34, 'Linda', 0x0F, '0x0F', 'Larry Wall' );
### Check to see which are numbers!
my @areNumbers = DBI::looks_like_number( @values );
for (my $i = 0; $i < @values; ++$i ) {
my $value = (defined $values[$i]) ? $values[$i] : "undef";
print "values[$i] -> $value ";
if ( defined $areNumbers[$i] ) {
if ( $areNumbers[$i] ) {
print "is a number!\n";
}
else {
print "is utterly unlike a number and should be
quoted!\n";
}
}
else {
print "is undefined!\n";
}
}
The results from this program illustrate how the values are treated and shows that hexadecimal values are not treated as numbers:
values[0] -> 333 is a number!
values[1] -> Choronzon is utterly unlike a number and should
be quoted!
values[2] -> Tim is utterly unlike a number and should
be quoted!
values[3] -> undef is undefined!
values[4] -> Alligator is utterly unlike a number and should
be quoted!
values[5] -> 1234.34 is a number!
values[6] -> Linda is utterly unlike a number and should
be quoted!
values[7] -> 15 is a number!
values[8] -> 0x0F is utterly unlike a number and should
be quoted!
values[9] -> Larry Wall is utterly unlike a number and should
be quoted!
The first And that brings us to the end of the introduction to DBI and its architecture. We'll be talking more on how to actually do stuff with DBI in the next chapter. |
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