From: "Chris Angell" <[EMAIL PROTECTED]>
> I have an idea for the int() function. I think it would be cool if it
> returned false/undefined when the argument passed to it is a
> whole number.
This is related to something I've been pondering about variables and typing.
Question A: In Perl6, how are types enforced? What would be the result
of trying to compile and run the following code:
my int $foo;
$foo = 'Fred';
The rest of this message assumes that the answer to A is "run time error".
I'd like to propose the following concept: by default, the result of the
above code would still be a runtime error, but with the use of a special
pragma/module, the result would be that the code runs as if $foo were an old
fashioned dynamically typed scalar. *However*, that scalar would still know
it's an integer trapped in a string's body. The same pragma/module that
allowed this sort of thing to happen would have a general purpose sub that
would indicate if a variable's value matches its typing:
unless match_type($fred) {
die 'The $foo variable must be an integer';
}
Some compile-time checks would be rearranged a little. The compiler would
refuse to allow you pass that variable to a declaration that wants some
other type of argument. However, if you let the variable get passed
unchecked to a sub that wants something else then you would get a run-time
error.
Here's one advantage to this approach. When I write an application in a
language that uses dynamic typing, I have to deal with the reality that
sometimes people type weird values into web forms. They put their names into
number fields, etc. To handle these types of errors I have to jump through
all kinds of hoops to deal with the weird values that come in. A lot of
times these hoops involve storing the input into a string variable, testing
the string, then assigning it again to the "real" variable. OTOH, with
dynamic typing, I still need to run a bunch of regexes against the variable
to test if it works. The proposed feature allows a simplified approach to
type testing.
-Miko
