Re^2: Programming in Perl without semicolon

Yuck! Use use vars.

{ use vars qw( @cache @n ) }
{@cache = (0, 1)}
sub fib {
    {push @n, shift}
    {return pop @n if $n[-1] < 2}
    {$cache [$n[-1]] ||= fib ($n[-1] - 1) + fib ($n[-1] - 2)}
    {return $cache[pop @n]}
}
[download]

Bonus: Doesn't confine you to the main namespace!

Now if we could only localize variables, we wouldn't need to manage our own stack.

{ use vars qw( @cache ) }
{@cache = (0, 1)}
sub fib {
    (local (our $n = shift)) && do {
        {return $n if $n < 2}
        {$cache[$n] ||= fib ($n - 1) + fib ($n - 2)}
        {return $cache[$n]}
    }
}
[download]

Bonus: Don't have to use use vars except for globals!

By the way, the body simplifies down to a single expression, and your cache initialiser is not needed.

{ use vars qw( @cache ) }
sub fib {
    (local (our $n) = shift), (
        $n < 2 ? $n : $cache[$n] ||= fib ($n - 1) + fib ($n - 2)
    )
}
[download]

Update: Replaced buggy
(local our $n = shift) && ...
with
(local (our $n) = shift) && ...

Comment on Re^2: Programming in Perl without semicolon Select or Download Code

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Re^3: Programming in Perl without semicolon by JavaFan (Canon) on Jan 31, 2009 at 08:37 UTC
Bonus: Doesn't confine you to the main namespace! That's only a bonus if you can switch packages without a semicolon. I haven't figured out how, except for the useless: `{package Foo}` [download] `(local our $n = shift) && do { ... }` [download] I'm surprised this works. I would have expected 'our' to be in effect after the statement, just like 'my'. (If you replace 'local our' with 'my', the code wouldn't compile under 'strict'). Unfortunally, it's not a general technique. It works here because 'fib(0)' is supposed to return '0'; the block isn't executed if the argument of the function is 0.	[reply] [d/l] [select]
Re^4: Programming in Perl without semicolon by ikegami (Patriarch) on Jan 31, 2009 at 18:54 UTC
That's only a bonus if you can switch packages without a semicolon. Oh yeah. Well, no bonus, but it still makes it more readable. I'm surprised this works. Me too, but it makes sense. It allows for `our $state = $next_states{$state};` [download] Unfortunally, it's not a general technique. Oops! Just replace the `and` op with a `list` op or replace the `sassign` op with an `aassign` op. `(local our $n = shift), ...` [download] or `(local (our $n) = shift) && ...` [download] The former is simpler. The latter has the advantage that it doesn't affect the return value in list context.	[reply] [d/l] [select]
Re^4: Programming in Perl without semicolon by JavaFan (Canon) on Jan 31, 2009 at 10:20 UTC
Unfortunally, it's not a general technique. It works here because 'fib(0)' is supposed to return '0'; the block isn't executed if the argument of the function is 0. But it can be written as: `local our ($n, $m) = (shift, 0)) && do { }` [download] and then it will always do the 'do'.	[reply] [d/l]


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