On Sat, Jun 22, 2024 at 8:04 PM Rowan Tommins [IMSoP] <imsop....@rwec.co.uk> wrote: > > On 21/06/2024 19:29, Larry Garfield wrote: > > Valid points. The line between validation and casting is a bit squishy, > as some casts can be forced (eg, string to int gives 0 sometimes), and > others just cannot (casting to an object). So would $a as > array<~int> be casting, validating, or both? > > > I think my concern is that both "x is T" and "x as T" read naturally as > *expressions*, where their main purpose is to evaluate to a result, and > side-effects are exceptional. > > From that point of view, we can give intuitive meaning to the following: > > - $foo is int => boolean; is $foo of type int? > - $foo is ~int => boolean; can $foo be "safely" cast to int? > - $foo as ~int => int; cast $foo to int (unless unsafe) > > But then what does this mean? > > - $foo as int => int; cast $foo to int if it's already an int !?
I've brought this up before, but I mostly see "as" being useful for static analysis. That's what I've mostly used it for C#, anyway. Logically, you know the type, but due to one-thing-or-another you can't "prove" the type is that type (such as foreach-arrays or dealing with results from user-code callbacks in library code). I want to be able to say "this is an int or else." [snip] Now ... that being said, I'm def not a fan of this "~" thing. It makes no sense to me. Semantically, what is the difference between "123", 123, and 123.0 other than how the bits are arranged in memory? If it can become an int -- regardless of how it is laid out in memory -- I expect to end up with an int as long as it is an integer. I would find it super annoying to have to fix that bug report with a single character, just because someone returned 123.0 instead of 123 because they rounded the number and I got the result from a callback. Further ~ means bitwise-not, so when you start mixing in literals ... what does it mean? $y = $x as ~1|~float; What is the value of $y? Is it the literal negative two, casted to the literal one (int), or casted a float?
