[Jprogramming] Three Simple Questions

[Dabrowski, Andrew John]

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?