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Why does this work: value each {x+y+z}[1;;],’enlist (2;enlist 3)
I understand the function and the projec`tion.
I’m wondering what is ” ,’ ” and why is it used here
Why do we enlist the list, and enlist 3 inside the list but not 2.
What is the “each” doing here, as far as I can see {x+y+z}[1;;],’enlist (2;enlist 3) is one thing in itself?
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1 Reply
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Might be best to deal with this in pieces
q)(2;3)
2 3
q)(2;enlist 3)
2
,3Here, the enlist is to prevent 2 and 3 concatenating into a simple list of longs.
The difference in the final output is an extra level of enlisting:
q)value each{x+y+z}[1;;],’enlist(2;3)
,6
q)value each{x+y+z}[1;;],’enlist(2;enlist 3)
6
q)type value each{x+y+z}[1;;],’enlist(2;enlist 3)
0h
q)type value each{x+y+z}[1;;],’enlist(2;3)
7hWhy the other enlist?
q){x+y+z}[1;;],'(2;enlist 3)
{x+y+z}[1;;] 2
{x+y+z}[1;;] 3
q){x+y+z}[1;;],’enlist(2;enlist 3)
{x+y+z}[1;;] 2 ,3In the first example, each element of the right-hand list (2 and ,3) is joined to the projection, which results in two projections being returned.
With the enlist, the right-hand side is now a one-element list (the element being (2;,3)). This is joined to the projection.
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