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Re: What is truth? (Curiosity corner)

by Anonymous Monk
on Dec 21, 2001 at 01:17 UTC ( #133616=note: print w/replies, xml ) Need Help??

in reply to What is truth? (Curiosity corner)

What about "0E0" for zero-but-true? Doesn't it work the same way?
perl -wle 'print 23+"0E0" if "0E0"' 23

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Re: Re: What is truth? (Curiosity corner)
by robin (Chaplain) on Dec 21, 2001 at 07:24 UTC
    Yeah, it does indeed. I'm not quite sure why "0 but true" is often preferred. Maybe because it's more explicit about its intention?
      "0E0" is used by the DBI (and DBD's) for eg. $sth->execute when the SQL-statement processed 0 rows but did not error.

      This allows constructions like my $rows=$sth->execute or die "SQL error" ( Of course this would be expressed better using $dbh->{RaiseError} = 1).

      The relevant part of the DBI documentation states:

      For a non-`SELECT' statement, `execute' returns the number of rows affected, if known. If no rows were affected, then `execute' returns "`0E0'", which Perl will treat as 0 but will regard as true. Note that it is not an error for no rows to be affected by a statement. If the number of rows affected is not known, then `execute' returns -1.

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