>>>>> "LW" == Larry Wall <[EMAIL PROTECTED]> writes:
LW> On Sat, Mar 15, 2003 at 05:32:41PM -0800, mlazzaro wrote:
LW> : So my reading is that it's not possible to specify 'required'
LW> : named parameters, unless we're completely missing something. My
LW> : first impulse is that it's not a big deal, because who's gonna
LW> : do that? My second impulse is... well... if I were writing a
LW> : big library with big, hairy methods, and wanted to *require* the
LW> : use of names for all params because the signatures are just too
LW> : baffling otherwise, I can sortof see wanting that... If, for
LW> : example, you are a purist who believes _all_ sub parameters
LW> : should be named, we might want Perl to nonjudgementally support
LW> : that particular neurosis. Bleah, dunno.
LW> Your reading is correct. It's possible to force the issue at run
LW> time, at least:
LW> sub foo(+$req = die 'You must supply a "req =>" argument') {...}
LW> or maybe
LW> sub foo(+$req = MUST) {...}
LW> where "MUST" could be something even more magical, possibly even
LW> recognized by the compiler, just as $CALLER::_ could be. But I'm
LW> not terribly interested in supporting that particular neurosis.
but if you declare required positionals and don't pass them all in even
by name, the compiler will detect that now via the signature. if the
caller knows the order and passes them in that way, and the module doc
says to pass them by name, then caller emptor. if the sub is documented
to be all pass by name and you don't do that, then you are to
blame. there is no need for more B&D here, just let the compiler check
the names passed in against the list in the sig.
this means that you have a more perl5 like experience IMO:
sub foo( $a, $b, $c ) { ... }
foo( 1, 2, 3 ) ;
foo( a => 1, c => 3, b => 4 ) ;
@args = ( a => 3, c => 4 ) ;
foo( b => 3, [EMAIL PROTECTED] ) ;
@args = ( a => 3 ) ;
foo( b => 3, [EMAIL PROTECTED], c => 5 ) ;
i think all of those should work (AFAIK they are ok with apoc6).
i like the ability to build up the pairs in an array or hash and
splatting that in the call. one good use is when you have extra
arguments optionally added to the arg list.
too often in p5 you see the args assigned to hash and then parsed out
with tedious runtime code or a module or sub that does it. i created
such a beast which describes all the attributes of an object with list
of hashes that have a name, required flag, default, and other
things. having the compiler do more of this checking would make it
easier to debug and remove a lot of runtime overhead.
having the required params in the first zone (positional) and then the
optional named args makes it also easier to manage required vs
optional. my current design has a whole attribute description flag
dedicated to 'required' and it only checks at runtime.
when you pass in named args with a splatted hash/array then you have to
defer checking to runtime if any required params aren't filled in
explicitly in the call. so the last two cases above lose some/all
compile time checking.
one issue is that you pass $b by position and the others by name. only
the earlier ones can be passed by position and later ones by name.
uri
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Uri Guttman ------ [EMAIL PROTECTED] -------- http://www.stemsystems.com
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