Re: false and nil

[James Darnley <james.darnley@...>]

On 2018-06-04 23:00, Sam Putman wrote:
> 
> 
> On Mon, Jun 4, 2018 at 1:54 PM, Hugo Musso Gualandi
> <hgualandi@inf.puc-rio.br <mailto:hgualandi@inf.puc-rio.br>> wrote:
> 
>     To make the boolean operators non-commutative you would need to give
>     up on short-circuiting evaluation. For example, consider:
> 
>         (i <= #xs and xs[i]:isgood())
> 
>     If you try to evaluate the right operand when the left one is false
>     (to check if it is nil or not) then xs[i] will evaluate to nil and
>     trying to call the isgood method will result in a runtime error.
> 
> 
> That... is persuasive.  I had worked out the simple ternaries but didn't
> get as far as this case. 
> 
> Ah well.  `nil or false` could still be nil, but to no remaining advantage.

This might not be directly related to your case but...  If you want to
turn any value into a boolean that still has the same truthiness then
use this:
> not not value

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