Re: Does this 'and' construct make sense?

[Richard Shann]

On Fri, 2015-03-06 at 08:25 +0100, Urs Liska wrote:
> I find
> 
> %% switch on debugging.
> #(if (and #t (defined? 'set-debug-cell-accesses!))
>    (set-debug-cell-accesses! 5000))
> 
> (found in init.ly)
> 
> strange.
> Wouldn't it be better ot simply remove the 'and' construct?
> #t evaluates to #t always, isn't it?

The terminology used in the manual is "#t evaluates to true". (And,
indeed #f is the only thing that evaluates to false). I think I then
found it tricky to find where in the manual this concept (true/false)
was explained, but came to understand it applies to the semantics of
"if" and "while".

> 
> Or is this one more Scheme subtlety I don't get?

so, I don't think so - the commonest cause is where someone starts with
(if (and Debug (defined? 'xxx))

and then decides not to have a separate Debug flag and replaces it in
bulk with #t

Richard