[Jprogramming] Three Simple Questions

[Henry Rich]

1.
    datatype 'abc'
literal
    3!:0 'abc'
2

Strings can also include 2- and 4-byte types, for which 3!:0 returns 
131072 and 262144; so a complete test for string would be

   (2 131072 262144 e.~ 3!:0)

2.  Correct.  You can return an empty value.

3. You don't need
num =. > num
etc.

Multiple assignment removes one level of boxing.  See

http://code.jsoftware.com/wiki/Vocabulary/Assignment#Multiple_Assignment

Henry Rich





On 12/1/2017 8:04 PM, Dabrowski, Andrew John wrote:
> 1. How does one test whether an object is string?
>
> 2. I now know that J doesn't support nullary functions.  It also seems
> that J doesn't allow functions that don't return any value (i.e. for the
> side effects), correct?
>
> 3. Suppose I want to define a dyadic function in which the y variable
> contains three values: a number, a vector, and a string. One way to do
> this would be to have y be a list of three boxes, say y = 13 ; 2 3 4 ;
> 'abcd' and parse y by
>
> fun =: dyad define
> 'num vec str' =. y
> num =. > num
> vec =. > vec
> str =. > str
> ...
> )
>
> Is this the idiomatic way to do it?  Is there a better way?
> ----------------------------------------------------------------------
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