first

First

*x

first is a primitive that returns the first item of a list

 *"abc"
"a"
 *(0 1;2 3;4 5)
0 1

or the first record of a table.

 t:+`a`b!(0 1;2 3)
 *t
`a`b!0 2

It has no effect on atoms, which can be used to check if a value is an atom.

 *12
12
 x~*x /is atom?

It treats a dictionary as the list of its values.

 d:`a`b!0 1
 *d
0

For empty collections, it returns the prototype:

 *!0
0N
 *""
" "