that significant subdomain would be {0,1}
in this domain,
• both 0&= and =&0 are synonymous with -.
while 1&= and =&1 are synonymous with ]
• 0&~: and ~:&0 are synonymous with ]
while 1&~: and ~:&1 are synonymous with -.
• on a sidenote,
⟨=~ x⟩ is =’s identity element here
⟨~:~ x⟩ is ~:’s identity element here
• so =/ (xs, x) is the same as =/ (xs, x, x, x)
and ~:/ (xs, x) is the same as ~:/ (xs, x, x, x)
put another way, if VOID is an empty structure,
we get the identity element by
(=/ VOID) which is the same as (=/ ;~ VOID)
and
(~:/ VOID) which is the same as (~:/ ;~ VOID)
[Elijah’s example was VOID =: '']
… but there are still people working as “programmers”
who obviously don’t know this
I’ve seen code segments featuring test clauses like
if (mybool == true)
embarrassingly often
Am 13.05.21 um 20:19 schrieb Roger Hui:
> Not for any y. For y in a significant subdomain of f.
>
>
> On Thu, May 13, 2021 at 11:10 AM Elijah Stone <[email protected]> wrote:
>
>> The identity elements for = and ~: are 1 and 0 respectively, as
>> illustrated by:
>>
>> =/''
>> 1
>> ~:/''
>> 0
>>
>>
>> I expect the identity element for some function f to be the value x such
>> that, for any y, y -: y f x. But this is clearly not the case here.
>>
>> Why not?
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
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