In some code ported from Ruby I have
grep "& @" ~/Router/router.nim
lcuts = v.vertex.neighbors - (lcuts & @[u.vertex, w.vertex])
Run
First I wrote lcuts & [u.vertex, w.vertex] but without the to seq operator it
does not compile. I wondered why concatenation of an seq and an array is not
supported. Of course typing the single @ in from of the array is not too much
work, but the question is if that is optimized or if a whole seq is allocated.
So I did a test:
proc main =
var s: seq[int]
for i in 0 .. 1e5.int:
#s.add(i)
s = s & @[i]
echo s[3] + s[^1]
main()
Run
While the program with add() takes milliseconds, it takes a few seconds with
the seq. I would say that this is a serious performance trap not only for
beginners. So maybe we should add concatenation of seq and array for std lib?
Tested with option -d:danger of course.
