How does this kbd function work? - kdb

Question

Would someone please explain the below function? How does the kdb utilize x here?
I changed the original function to "func" I know it uses the queries assigned in que to query both functions. The problem is I don't know how those x 0 and and x 0 1 work here. I know 0 is the index 1 and 1 is the index 2 and x is the parameter.
svcs:`TEST:1`TEST:2
que: (`$"select count sym from trades";`$"select sum size from trades")
{func[x 0;string x 1],x 0 1}each svcs cross que

Answer 1

x is being passed in as a two element list "each" time the function is called.
Forget about the func description for now and just add in some logging to see things more clearly:
q)svcs cross que
TEST:1 select count sym from trades
TEST:1 select sum size from trades
TEST:2 select count sym from trades
TEST:2 select sum size from trades
q){show enlist "x 0 is ",string x 0;show enlist "x 1 is ",string x 1;show raze "
x 0 1 is ",(string x 0)," & ", (string x 1)}each svcs cross que;
"x 0 is TEST:1"
"x 1 is select count sym from trades"
"x 0 1 is TEST:1 & select count sym from trades"
"x 0 is TEST:1"
"x 1 is select sum size from trades"
"x 0 1 is TEST:1 & select sum size from trades"
"x 0 is TEST:2"
"x 1 is select count sym from trades"
"x 0 1 is TEST:2 & select count sym from trades"
"x 0 is TEST:2"
"x 1 is select sum size from trades"
"x 0 1 is TEST:2 & select sum size from trades"
Or an individual example:
q)x:(`TEST:1;`$"select count sym from trades")
q)x 0
`TEST:1
q)x 1
`select count sym from trades
q)x 0 1
`TEST:1`select count sym from trades
x 0 1 indexes and retrieves both the first and second element (returning

Answer 2

You're right and x 0 or x 1 is the same as x[0] or x[1] (see the link below on indexing lists), except perhaps the problem is that it isn't obvious what x is.
Because of the adverb each the function is executed four times, once for each item in svcs cross que
See;
q)count svcs cross que
4
And then each item in svcs cross que has two items.
q)count each svcs cross que
2 2 2 2
So in the first execution, x is the first item of svcs cross que and so on.
q)first svcs cross que
`TEST:1`select count sym from trades
q)(first svcs cross que) 0
`TEST:1
q)(first svcs cross que) 1
`select count sym from trades
q)(first svcs cross que) 0 1
`TEST:1`select count sym from trades
Reference
http://code.kx.com/q4m3/6_Functions/#671-monadic-each
http://code.kx.com/q4m3/3_Lists/#34-indexing