Define global variable within a function in q kdb - kdb

Question

I can see two ways to define a global variable from a function in q.
Using ::
q){gv::10}[]
q)gv /- 10
Using set
q){`gv set 20}[]
q)gv /- 20
There is a catch with set i.e. if a global variable already has a symbol assigned to it, then the value which is assigned to global variable within the function is assigned to the symbol which is assigned to global variable.
q)gv:`t
q){gv set 20}[]
`t
q)gv
`t
q)t
20
Can someone please explain me which is the better way (set or ::) to define a global variable within a function and why is it better?

Answer 1

There is no "better" really - but set has the advantage of assigning to a variable name which is itself a variable (as you showed in your example).
I'm confused about your confusion in the last example though......if you wanted 20 to be assigned to a global called gv then you should put a backtick in front of gv, aka `gv set 20; and conversely if you wanted 20 to be assigned to the symbol/name that gv contains then don't use the backtick, aka gv set 20;
Final point to note is that you can also create globals in non-root directories/namespaces using a single colon assignment
q){.this.that:1;}[]
q)
q).this
| ::
that| 1