[Jprogramming] Floor of infinity

[Skip Cave]

What I'm really looking for, is a verb that finds integers in a list:

datatype 2.5

floating

datatype 3

integer

datatype __

floating


So J considers __ as "floating"


 So I want a verb "isinteger" that marks the integers in a vector, where __
is in the list, and is considered floating:

  isinteger 1 2.5 __ 3 4.5 6
1 0 0 1 0 1

And maybe the inverse also:

isfloating 1 2.5 __ 3 4.5 6

0 1 1 0 1 0


My (=<,) doesn't do it:

(=<.)1 2.5 __ 3 4.5 6

1 0 1 1 0 1


So what would "isinteger" look like?


Skip


Skip Cave
Cave Consulting LLC


On Sun, Aug 2, 2020 at 1:44 AM Skip Cave <skip at caveconsulting.com> wrote:

> I use the (=<.) verb to find integers in a list:
>
>
> * (=<.)1 2.5 2.7 3 4.5 6*
>
> *1 0 0 1 0 1*
>
> * (#~(=<.))1 2.5 2.7 3 4.5 6*
>
> *1 3 6*
>
> I ran across an interesting result when infinity is in the list:
>
> * (=<.)1 2.5 __ 3 4.5 6*
>
> *1 0 1 1 0 1*
>
> * (#~(=<.))1 2.5 __ 3 4.5 6*
>
> *1 __ 3 6*
>
>
> So J is saying that the floor of infinity is infinity (and the ceiling of
> infinity is also infinity). Since infinity is not a number, it would seem
> that an error should be generated when taking the floor of infinity, or
> perhaps NAN, or a zero? In any case, this messes up my nice integer-finding
> verb. Is the\re a mathematical justification for defining the floor of
> infinity to be infinity?
> https://math.stackexchange.com/questions/981708/limit-of-floor-function-when-x-goes-infinity
>
>
> Skip
>
>
> Skip Cave
> Cave Consulting LLC
>