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make unzip faster: seq[i]=val can be 7X faster than seq.add(elem) (#13448)

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Timothee Cour 2020-02-21 08:26:52 -08:00 • committed by GitHub
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1 changed files with 5 additions and 5 deletions
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10
lib/pure/collections/sequtils.nim
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@ -290,11 +290,11 @@ proc unzip*[S, T](s: openArray[(S, T)]): (seq[S], seq[T]) {.since: (1, 1).} =
unzipped2 = @['a', 'b', 'c'] unzipped2 = @['a', 'b', 'c']
assert zipped.unzip() == (unzipped1, unzipped2) assert zipped.unzip() == (unzipped1, unzipped2)
assert zip(unzipped1, unzipped2).unzip() == (unzipped1, unzipped2) assert zip(unzipped1, unzipped2).unzip() == (unzipped1, unzipped2)
result[0] = newSeqOfCap[S](s.len) result[0] = newSeq[S](s.len)
result[1] = newSeqOfCap[T](s.len) result[1] = newSeq[T](s.len)
for elem in s: for i in 0..<s.len:
result[0].add(elem[0]) result[0][i] = s[i][0]
result[1].add(elem[1]) result[1][i] = s[i][1]
proc distribute*[T](s: seq[T], num: Positive, spread = true): seq[seq[T]] = proc distribute*[T](s: seq[T], num: Positive, spread = true): seq[seq[T]] =
## Splits and distributes a sequence `s` into `num` sub-sequences. ## Splits and distributes a sequence `s` into `num` sub-sequences.