Re^3: Named Subroutine Parameters: Compile-time errors vs. Run-time warnings

[shmem]

Still, at least it's not the worst mistake I made in PBP. ;-)

Uh-oh. Whats next? Have a list? ;-)

I stand by the overall recommendation though. Error messages that point users to the right place are definitely worth the (tiny) overhead of passing named args in a hash.

Definitely. The recommendation of passing named args in a hash is fine, the one of the MTOW you promote TDI is, if not wrong, then sub-optimal.

my %hash = (
    foo => 1,
    bar => quux($blorf),
);
my $result = frobnitz(\%hash); # ok
my $result = frobnitz( %hash); # also ok

# ---

my $hashref = (
    foo => 1,
    bar => quux($blorf),
);
my $result = frobnitz( $hashref); # ok

# ---

frobnitz( { foo => 1, bar => scalar bar($quux) } ); # not ok

In the above examples, both of the costly structures for %hash and $hashref are allocated at the pad of the current scope and populated at run time. In the last example, that structures are set up and teared down at every call to frobnitz() :

use Devel::Peek;

sub f{
    Dump $_[0]
};
f( {o=>1} ) for 1..3;
__END__
SV = RV(0x8c17080) at 0x8c17074
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0x8bfd7a4
  SV = PVHV(0x8c02d04) at 0x8bfd7a4
    REFCNT = 1
    FLAGS = (SHAREKEYS)
    ARRAY = 0x8c1bb0c  (0:7, 1:1)
    hash quality = 100.0%
    KEYS = 1
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "o" HASH = 0xc74f0e7f
    SV = IV(0x8c17060) at 0x8c17064
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 1
SV = RV(0x8c17070) at 0x8c17064
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0x8c17074
  SV = PVHV(0x8c02d04) at 0x8c17074
    REFCNT = 1
    FLAGS = (SHAREKEYS)
    ARRAY = 0x8c1bb0c  (0:7, 1:1)
    hash quality = 100.0%
    KEYS = 1
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "o" HASH = 0xc74f0e7f
    SV = IV(0x8bfd7a0) at 0x8bfd7a4
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 1
SV = RV(0x8bfd7b0) at 0x8bfd7a4
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0x8c17064
  SV = PVHV(0x8c02d04) at 0x8c17064
    REFCNT = 1
    FLAGS = (SHAREKEYS)
    ARRAY = 0x8c1bb0c  (0:7, 1:1)
    hash quality = 100.0%
    KEYS = 1
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "o" HASH = 0xc74f0e7f
    SV = IV(0x8c17070) at 0x8c17074
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 1

Some of the above pointer being equal is just an artefact of the subsequent call of the same sub (I guess here).