Fix initial value handling with flatten transducer #34369
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There was a bug in initial value handling of `FlatteningRF` and the
following example failed:
@test mapfoldl(
x -> (x, x),
((a, b), (c, d)) -> (min(a, c), max(b, d)),
Iterators.flatten((1:2, 3:4)),
) == (1, 4)
This is because `BottomRF(op.rf)` was called inside `FlatteningRF`
where `op.rf` is already a "non-bottom" reducing function; here it's a
`MappingRF`. As `BottomRF(rf)` forwards anything on the second
argument on the first invocation as the first argument (accumulator)
of the next calls, we need to make sure that this value is processed
through `MappingRF` in the above example. However, if we do
`BottomRF(op.rf)` where `op.rf` is a `MappingRF`, this `BottomRF`
bypasses any processing that has to happen in `op.rf`.
|
Well, the tests pass, so I believe you :) |
KristofferC
pushed a commit
that referenced
this pull request
Jan 15, 2020
There was a bug in initial value handling of `FlatteningRF` and the
following example failed:
@test mapfoldl(
x -> (x, x),
((a, b), (c, d)) -> (min(a, c), max(b, d)),
Iterators.flatten((1:2, 3:4)),
) == (1, 4)
This is because `BottomRF(op.rf)` was called inside `FlatteningRF`
where `op.rf` is already a "non-bottom" reducing function; here it's a
`MappingRF`. As `BottomRF(rf)` forwards anything on the second
argument on the first invocation as the first argument (accumulator)
of the next calls, we need to make sure that this value is processed
through `MappingRF` in the above example. However, if we do
`BottomRF(op.rf)` where `op.rf` is a `MappingRF`, this `BottomRF`
bypasses any processing that has to happen in `op.rf`.
(cherry picked from commit 0ee3264)
KristofferC
pushed a commit
that referenced
this pull request
Jan 15, 2020
There was a bug in initial value handling of `FlatteningRF` and the
following example failed:
@test mapfoldl(
x -> (x, x),
((a, b), (c, d)) -> (min(a, c), max(b, d)),
Iterators.flatten((1:2, 3:4)),
) == (1, 4)
This is because `BottomRF(op.rf)` was called inside `FlatteningRF`
where `op.rf` is already a "non-bottom" reducing function; here it's a
`MappingRF`. As `BottomRF(rf)` forwards anything on the second
argument on the first invocation as the first argument (accumulator)
of the next calls, we need to make sure that this value is processed
through `MappingRF` in the above example. However, if we do
`BottomRF(op.rf)` where `op.rf` is a `MappingRF`, this `BottomRF`
bypasses any processing that has to happen in `op.rf`.
(cherry picked from commit 0ee3264)
|
Any thoughts on who to review? |
|
It's already merged :P |
|
Yeah, took my browser a while to figure that out, by which point I'd already commented. |
KristofferC
pushed a commit
that referenced
this pull request
Jan 17, 2020
There was a bug in initial value handling of `FlatteningRF` and the
following example failed:
@test mapfoldl(
x -> (x, x),
((a, b), (c, d)) -> (min(a, c), max(b, d)),
Iterators.flatten((1:2, 3:4)),
) == (1, 4)
This is because `BottomRF(op.rf)` was called inside `FlatteningRF`
where `op.rf` is already a "non-bottom" reducing function; here it's a
`MappingRF`. As `BottomRF(rf)` forwards anything on the second
argument on the first invocation as the first argument (accumulator)
of the next calls, we need to make sure that this value is processed
through `MappingRF` in the above example. However, if we do
`BottomRF(op.rf)` where `op.rf` is a `MappingRF`, this `BottomRF`
bypasses any processing that has to happen in `op.rf`.
(cherry picked from commit 0ee3264)
KristofferC
pushed a commit
that referenced
this pull request
Apr 11, 2020
There was a bug in initial value handling of `FlatteningRF` and the
following example failed:
@test mapfoldl(
x -> (x, x),
((a, b), (c, d)) -> (min(a, c), max(b, d)),
Iterators.flatten((1:2, 3:4)),
) == (1, 4)
This is because `BottomRF(op.rf)` was called inside `FlatteningRF`
where `op.rf` is already a "non-bottom" reducing function; here it's a
`MappingRF`. As `BottomRF(rf)` forwards anything on the second
argument on the first invocation as the first argument (accumulator)
of the next calls, we need to make sure that this value is processed
through `MappingRF` in the above example. However, if we do
`BottomRF(op.rf)` where `op.rf` is a `MappingRF`, this `BottomRF`
bypasses any processing that has to happen in `op.rf`.
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There was a bug in initial value handling of
FlatteningRFand thefollowing example failed:
This is because
BottomRF(op.rf)was called insideFlatteningRFwhere
op.rfis already a "non-bottom" reducing function; here it's aMappingRF. AsBottomRF(rf)forwards anything on the secondargument on the first invocation as the first argument (accumulator)
of the next calls, we need to make sure that this value is processed
through
MappingRFin the above example. However, if we doBottomRF(op.rf)whereop.rfis aMappingRF, thisBottomRFbypasses any processing that has to happen in
op.rf.