Skip the warm-up readings
Requirement
A temperature probe reads low while it warms up. Drop the leading readings below 20.0 °C, format everything after the first live reading — including later dips, which are real data — and print how many readings survived. The data is in the code; both versions must print the lines shown under Expected output.
Expected output
Live: 21.4 °C Live: 20.9 °C Live: 18.7 °C Live: 22.3 °C Live: 23.0 °C Kept 5 of 8 readings
Side by side
RxDart
FxDart
Why they differ
They don't, and that is the finding. skipWhile and
dropWhile are the same one-way gate: it discards while
the predicate holds, opens permanently at the first failure, and
never closes again — which is why the 18.7 °C dip after warm-up
survives on both sides. This is a gate over sequence position,
not value, and both models have a name for it.
Worth noticing: the RxDart panel is pure dart:async on
this job — skipWhile, map and
toList all ship on core Stream, so RxDart's
import earns nothing here. That is what tier-1 overlap looks like
from the other direction: sometimes the shared vocabulary lives in
the platform itself. The only leftover is the delivery model — an
async main and an await to collect what a
pull chain returns as a plain value, no event loop involved. A tie.
Benchmark
N = 100
Time Tie
Peak memory Tie
N = 1,000,000
Time FxDart wins
Peak memory RxDart wins
Bars are medians of repeated timed iterations in fresh processes per side (small N is batched for timer resolution). Sides within 5% of each other — or within 0.6 ms, a difference no person can perceive — count as a tie; close relative races are re-measured up to 5 runs. In an app, anything under a few milliseconds is invisible to the user regardless of which bar is shorter. Memory is peak process RSS. The Dart VM and the dataset are identical on both sides, so the difference between the two bars is what the pipeline itself holds onto.