This is another great example of why I love this list. :o]
I live in GA, so far out in the boonies that I can't get cable or
broadband at *all* except for by satellite. I've stopped trying to
explain what I do, because I start saying things like this, and they
glaze and visibly regret it, lol....
Now I just tell them my official job title is "computer monkey".
That works pretty well. :)
But so that this post isn't (hopefully) entirely hot air,
How does this sort of adverbial typecasting relate back to compile
time typing? The old my Dog $spot thing?
There seems to be a significant relationship, but I can't wrap my head
around where the underlying mechanics might be usefully applied.
<goes off to reread the synopses/exegeses et alii>
--- Ryan Richter <[EMAIL PROTECTED]> wrote:
> On Tue, Dec 04, 2007 at 07:39:16AM -0800, Larry Wall wrote:
> > On Sun, Oct 07, 2007 at 03:01:06PM -0600, David Green wrote:
> > > What happened to the suggestion of using ` to designate units?
> >
> > It's kinda caught between two other notions. On the one hand,
> > we're trying to reserve ` for user definition, in part because it's
> > so difficult to tell from ' in many fonts so we're avoiding it for
> > standard usage. On the other hand, it's not clear that units
> aren't
> > generally just simple multiplication by a scaling factor: 1*in,
> where
> > 1*in == 2.54*cm, for instance. Units could also be viewed as type
> > conversion, which would give us kg(1) and 1.kg as conversion forms
> > in current Perl 6. Since 1.kg is essentially using the units as a
> > postfix, presumably the 1kg form could also work on literals, just
> as
> > we currently allow 1i to convert 1 to i via the postfix:<i>
> operator.
> > (And I suppose there's a sense in which 10e-2 is specifying the
> > scaling factor of the left side explicitly.)
> >
> > In any case, though, if we treated them as type names rather than
> > just methods, we'd probably want to require predeclaration of unit
> > names since a type name like "kg" or "in" or "fortnight" could
> easily
> > collide with a user-defined routine. Or maybe they still want some
> > special sigil-ish mark to stay in their own namespace. Dunno. I
> don't
> > think we have to solve that for 6.0.0 in any case, especially if we
> > require predeclaration of which unit names are wanted, in which
> case
> > there might just be a units pragma that can pull in selections of
> > the predefined units:
> >
> > use units :cgs, :nasa, <μfortnight gibibyte>;
> > my newton $thrust = 42.lbf;
> >
> > But with a sigilish mark we could just pull in all the units from
> > /usr/share/units.dat, I suppose.
>
> I don't know if I ever mentioned it on the mailing list, but a while
> back I did some work on a units module that uses units.dat
> (examples/rules/unitsdat-grammar.pm in the pugs repo). I think
> that a simple postfix syntax (e.g.) doesn't give you the ability to
> specify the kind of composite units that are common in scientific
> applications where units are heavily used (e.g. Gauss per square root
> Hertz). Those kind of units also rule out simple type-based units,
> e.g.
> having roles for length, mass, etc. - you can't do a role to the -7/3
> power. I settled on a syntax that allows a mini-language similar to
> units(1):
>
> 9.8.:as<m / s ** 2>
> $field_noise.:as<gauss / sqrt(Hz)>
>
> But someone may be able to come up with something better. My
> implementation does unit type-checking at runtime, but compile-time
> checking would be much nicer where possible. It would also be cool
> to
> be able to define roles that can represent themselves in several
> different units:
>
> role Photon does NumUnit { ??? }
> my Photon $p .=new( energy => 42.:as<eV> );
> say "energy is $p.:as<zJ> zeptojoules";
> say "wavelength is $p.:as<angstrom> â«";
> say "frequency is $p.:as<THz> THz";
>
> -ryan
>
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