|
Perl4-to-Perl5 traps having to do with numerical operators, operands, or output from same.
- * Numerical
-
Formatted output and significant digits. In general, Perl 5 tries to be more precise. For
example, on a Solaris Sparc:
print 7.373504 - 0, "\n";
printf "-.18f\n", 7.373504 - 0;
# Perl4 prints:
7.3750399999999996141
7.375039999999999614
# Perl5 prints:
7.373504
7.375039999999999614
|
|
Notice how the first result looks better in Perl 5.
Your results may vary, since your floating point formatting routines and even floating
point format may be slightly different.
- * Numerical
-
This specific item has been deleted. It demonstrated how the auto-increment operator
would not catch when a number went over the signed int limit. Fixed in version 5.003_04. But
always be wary when using large integers. If in doubt:
- * Numerical
-
Assignment of return values from numeric equality tests does not work in perl5 when the
test evaluates to false (0). Logical tests now return a null, instead of 0
$p = ($test == 1);
print $p,"\n";
# perl4 prints: 0
# perl5 prints:
|
|
Also see "General
Regular Expression Traps using s///, etc." for another example of this new
feature...
- * Bitwise string ops
-
When bitwise operators which can operate upon either numbers or strings (& | ^
~) are given only strings as arguments, perl4 would treat the operands as bitstrings
so long as the program contained a call to the vec() function. perl5 treats the
string operands as bitstrings. (See perlop/Bitwise
String Operators for more details.)
$fred = "10";
$barney = "12";
$betty = $fred & $barney;
print "$betty\n";
# Uncomment the next line to change perl4's behavior
# ($dummy) = vec("dummy", 0, 0);
# Perl4 prints:
8
# Perl5 prints:
10
# If vec() is used anywhere in the program, both print:
10
|
|
|
|
