Re: Declarations of constants
Adam Kennedy wrote:
Forgive my ignorance here, but for all of these different ways of doing
constants, will they all optimize (including partial
evaluation/currying) at compile/build/init/run-time?
my $gravity is constant = 10; # One significant figure
sub time_to_ground ($height, $accel) {
...acceleration math...
}
my $time = time_to_ground( 500, $gravity );
... thus simplifying internally to
my $time = 1234;
No. But you could get the effect by explicitly asking for time_to_ground() to
be called at compile-time:
my $gravity is constant = 10; # One significant figure
macro time_to_ground ($height, $accel) {
...acceleration math...
}
my $time = time_to_ground( 500, $gravity );
Damian
Re: Declarations of constants
[EMAIL PROTECTED] (Adam Kennedy) writes:
> Forgive my ignorance here, but for all of these different ways of
> doing constants, will they all optimize (including partial
> evaluation/currying) at compile/build/init/run-time?
Gosh, I hope not.
> my $gravity is constant = 10; # One significant figure
> sub time_to_ground ($height, $accel) {
> ...acceleration math...
> }
The ability to play around with the working of &time_to_ground before it
runs is one of the things I like about Perl.
--
A language that doesn't have everything is actually easier to program
in than some that do.
-- Dennis M. Ritchie
Re: Declarations of constants
Ingo Blechschmidt wrote:
Hi,
# Way 1
my $MEANING_OF_LIFE is constant = 42;
Forgive my ignorance here, but for all of these different ways of doing
constants, will they all optimize (including partial
evaluation/currying) at compile/build/init/run-time?
my $gravity is constant = 10; # One significant figure
sub time_to_ground ($height, $accel) {
...acceleration math...
}
my $time = time_to_ground( 500, $gravity );
... thus simplifying internally to
my $time = 1234;
Adam K
Re: Declarations of constants
Hi,
"TSa (Thomas Sandlaß)" wrote:
> Ingo Blechschmidt wrote:
>> Or did you simply forget the braces around 42? :)
>
> No, it was intented for seeing what the reactions will be :)
:)
> Just using &foo as unsigiled variable. This might need
>
> my &foo is rw;
I don't think this will DWYW, as firstly "is rw" is the default
on vars declared with my(), and secondly &foo will be undef, not some
kind of Proxy object. To do what you want, you'd have to write (I
think):
my &foo = new_codeless_lvalue_sub();
sub new_codeless_lvalue_sub {
my $var;
return {
new Proxy: FETCH => { $var }, STORE => -> $new { $var = $new };
};
}
> But then I presume you could say:
>
> foo = 17;
> if foo < 8
> {
> @a[foo] = 8;
> }
>
> We could call that a codeless lvalue sub ;)
This indeed looks very slick! I wouldn't use it for normal vars, though.
--Ingo
--
Linux, the choice of a GNU | The next statement is not true.
generation on a dual AMD | The previous statement is true.
Athlon!|
Re: Declarations of constants
Ingo Blechschmidt wrote:
is that allowed (as 42 is a Num (or an Int), not a Code)?
I don't know, but guess not.
Do (most of) the basic types morph themselves into Codes, when needed?
I don't consider it type morphing. If your examples parse
at all they will be dispatched as usual
say 42();# 42?
&postfix:<.( )>:( Int :)
say "Perl"();# Perl?
&postfix:<.( )>:( Str :)
say [1,2,3].does(Code) # true?
Depends on the type of [] which is Ref of Array or so.
But I think it should be false.
Or did you simply forget the braces around 42? :)
No, it was intented for seeing what the reactions will be :)
Just using &foo as unsigiled variable. This might need
my &foo is rw;
But then I presume you could say:
foo = 17;
if foo < 8
{
@a[foo] = 8;
}
We could call that a codeless lvalue sub ;)
--
TSa (Thomas Sandlaß)
Re: Declarations of constants
Hi, "TSa (Thomas Sandlaß)" wrote: > my &MEANING_OF_LIVE = 42; # But might be considered evil sigilless > mode is that allowed (as 42 is a Num (or an Int), not a Code)? Do (most of) the basic types morph themselves into Codes, when needed? say 42();# 42? say "Perl"();# Perl? say [1,2,3].does(Code) # true? Or did you simply forget the braces around 42? :) --Ingo -- Linux, the choice of a GNU | Wer die Freiheit aufgibt, um Sicherheit zu generation on a dual AMD | gewinnen, der wird am Ende beides Athlon!| verlieren" -- Benjamin Franklin
Re: Declarations of constants
Ingo Blechschmidt wrote: # Please add more ways :) enum ; my &MEANING_OF_LIVE = 42; # But might be considered evil sigilless mode -- TSa (Thomas Sandlaß)
