Re: ?-suffix for booleans... good-idea? or bad-idea?

[Neil Jerram <neil@ossau.homelinux.net>]

I'm also not sure.  In the past I've written code with an 'xxx?' 
variable, and then added a procedure to set it, giving 'set-xxx?!' - 
which is not exactly elegant.

Also I'm not sure it's best practice to have many 
variables/attributes/parameters with boolean values, as this can lead to 
code that has too many opaque uses of #t and #f.  (I.e. it's often 
unclear, at the point of use, what each #t or #f means.)  It might be 
better to refactor to something with non-boolean values, e.g. from

    (set! red? #t)
    (set! narrow?#t)

to

    (set! properties '(red narrow))

And in that case the question about '?' would disappear.

Regards,
       Neil


On 25/04/17 04:43, Alex Vong wrote:
> Good question! I can't decide as well. I want to know how people think
> about it.
>
> In a lazy language, a variable is a 0-ary thunk, while a predicate is a
> 1-ary thunk. Since they are really just special case of a general thing,
> it make sense to use foo? for both cases. But we all know guile is not
> lazy, so I really don't know what to do.
>
> Christopher Allan Webber <cwebber@dustycloud.org> writes:
>
>> Hello everyone!  Here's a little bikeshed for us to paint.
>>
>> I've noticed that it's common in Guile modules to use "foo?" for
>> variable names involving booleans.  It's tempting, because this looks
>> an awful lot like you're asking a question... and it's also common
>> for this even to be keyword arguments to procedures, etc.
>>
>> But is it a good idea?  I thought "foo?" was supposed to be for
>> predicates, as a nicer version of the "foo-p" predicate convention in
>> other non-scheme lisps.  I can't imagine other lisps doing "foo-p" for
>> just variables with boolean values.
>>
>> On the other hand, once you start adding ? to the end of boolean'y
>> things, it *does* become tempting to put them at the end of boolean
>> variables and arguments.  It looks pretty nice.
>>
>> What do people think?  I'm struggling with deciding what's the right
>> thing for my own code, but leaning towards "we shouldn't use the ?
>> suffix for just boolean values".
>>
>>   - Chris