Hi Rick,
Let's look at the explicit form (x*y) % (x-y), which would be identical
in S. When you put this into tacet programming it drops the y:
((x*) % (x-)) . I am not certain about this, but doesn't "[" bring in the
left
argument? This would make the tacit expression: ([ @: *) % ([ @: -)).
I don't think that's any easier than (([)*)%([)-
Don
----- Original Message -----
From: "Sherlock, Ric" <[email protected]>
To: "Chat forum" <[email protected]>
Sent: Thursday, April 23, 2009 7:59 AM
Subject: Re: [Jchat] Language S
>> From: Don Watson
>>
>> Thanks Ric, that helps.
>>
>> You are right. I haven't addressed the issue of the (DDD) fork,
>> where
>> the presence of a left argument establishes that the outer two verbs
>> are
>> dyadic. In S this would be: (([)*)%([)- . I agree that this
>> contains
>> extra parentheses. However, it does follow the right to left rule.The
>> expression (([)*) is evaluated before the % because of its parentheses.
>> In
>> S, a dyadic verb is always identified by a noun or a parentheses on its
>> immediate left - as is true in non-tacit J programming. This is why an
>> extra
>> tacit form is not needed.
>>
>> 7 (* % -) 3 2 does not follow the right to left rule because the *
>> is
>> not enclosed in parentheses, but is used before the % to its right.
>
> So parentheses are allowed to change the order of execution but still
> "follow the left to right rule", but other exceptions aren't?
>
> Are you seriously proposing that students and teachers are more likely to
> identify with:
> (([)*)%([)-
> than the following explicit J expression?
> (x*y) % (x-y)
>
> I'd leave the tacit (* % -) for later although I'd still consider it
> preferable to the first expression.
>
> Maybe the quest to simplify things by strictly following the right to left
> rule (except for parentheses) is getting in the road of your stated
> objective of creating a notation that is more useful for teaching maths?
>
>
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