On 10/6/05, Luke Palmer <[EMAIL PROTECTED]> wrote:
> So we're in line one of a Perl program, with static typing/inference
> disabled (or at least inference *checking* disabled; perl may still
> use it for optimization). When do the following die: compile time
> (which includes CHECK time), run time, or never?
This is just my opinions as a Perl programmer in the trenches. I would
expect Typed variables to auto-coerce themselves, but not impose
fatality. Predictable auto-coercion would be nifty in quick-and-dirty
programs.
Ignore my advice at will -- nobody's required to use Types in their
own code, so there's no need for them to be universally valuable.
However, since I expect builtins and all standard functions to have
fully declared Type signatures, consider how these decisions would
affect _every_ program, before ordering the summary execution of
everyone's poor little Perl script.
> my Array $a = 97; # dies eventually, but when?
Runtime -- cannot coerce Int value to Array
> my Int $b = 3.1415; # dies at all?
Doesn't die, $b == 3. Int scalars should coerce anything which can be
&prefix:<+>'d.
> sub foo (Int $arg) {...}
> foo("hello"); # should die at the latest when foo() is called
$arg should be undef but Exception::InvalidInteger("Str value 'hello'
cannot be coerced to an Int at $?LINE")
> sub bar (Int $arg --> Str) {...}
> foo(bar(42));
If bar returns a Str ~~ /<Perl6::Grammar::Int>/, it gets coerced;
otherwise, undef but Exception
> sub static (Code $code, Array $elems --> Array) {
> [ $elems.map:{ $code($_) } ]
> }
> sub dynamic ($code, $elems) {
> [ $elems.map:{ $code($_) } ]
> }
> static({ $_+1 }, dynamic("notcode", [1,2,3,4,5]));
die "Str value 'notcode' cannot be called as a Sub reference -- have
you asked Larry how to make a symbolic function call, lately?";
> dynamic("notcode", static({ $_+1 }, [1,2,3,4,5]));
Same.
Just my 2ยข
Ashley Winters
