(q/kdb+) Generating an automated list - kdb

Question

Example 1)
I have the code below
5#10+1*2
that generates
index value
0 12
1 12
2 12
3 12
4 12
How can I replace the number "1" by the index?
then generating
5#10+index*2
index value
0 10
1 12
2 14
3 16
4 18
update Example 2)
Now, if I have, let's say
mult:5;
t:select from ([]numC:1 3 6 4 1;[]s:50 16 53 6 33);
update lst:(numC#'s) from t
the last update will generate
numC s lst
1 50 50
3 16 16 16 16
6 53 53 53 53 53 53 53
4 6 6 6 6 6
1 33 33
How can I generate the "lst" column as per below?
numC s lst
1 50 50+0*mult
3 16 16+0*mult 16+1*mult 16+2*mult
6 53 53+0*mult 53+1*mult 53+2*mult 53+3*mult 53+4*mult 53+5*mult
4 6 6+0*mult 6+1*mult 6+2*mult 6+3*mult
1 33 33+0*mult
I tried something like
update lst:(numC#'s + (til numC)*mult) from t
but I am getting an error
ERROR: 'type
Thanks vm

Answer 1

Is this what you're looking for:
q)x:5
q)x#10+(til x)*2
10 12 14 16 18
http://code.kx.com/q/ref/arith-integer/#til

Answer 2

You can remove take # and use til to simplify to:
q)10+2*til 5
10 12 14 16 18
Using til will create a list of a list of 5 elements (0->4), so you will not need take 5 elements from the resulting list. Take will only be required if your list of indices is greater than 5.
Update:
For your second example the following should work:
q)update lst:{y+x*til z}'[mult;s;numC] from t
q)update lst:s+mult*til each numC from t
numC s lst
-------------------------
1 50 ,50
3 16 16 21 26
6 53 53 58 63 68 73 78
4 6 6 11 16 21
1 33 ,33

Answer 3

There are many ways with which we can get achieve this:
1) 10+2*til 5
2) (2*til 5) + 10
/ take operator: The dyadic take function creates lists. The left argument specifies the count and shape and the right argument provides the data.
It is useful for selecting from the front or end of a list.
https://code.kx.com/wiki/Reference/NumberSign
q)5#0 1 2 3 4 5 6 7 8 / take the first 5 items
0 1 2 3 4
q)-5#0 1 2 3 4 5 6 7 8 / take the last 5 elements
4 5 6 7 8
use take operator # only when it is required.
say we have 10 elements, of which we need five on output, then we can use:
5#10+2*til 10
/ The til function takes a non-negative integer argument X and returns the first X integers