`Psar::is_ready` previously returned `self.initialised`, which flips to
`true` *after* the seed candle — but the seed candle itself returns
`None`. The contract every other indicator honours is
`is_ready() == true` ↔ "the most recent update produced (or could
produce) a real value". Streaming consumers writing
`if ind.is_ready() { use(ind.update(c)?) }` would hit an unexpected
`None` on the first post-seed update.
Fix: add a `has_emitted: bool` field that flips on the first
`Some(sar)` return; `is_ready` now reads that. New test
`is_ready_only_after_first_some_value` pins the contract.
While in the same file, `reset()` is corrected to restore the compute
fields (`prev_high`, `prev_low`, `sar`, `ep`) to `f64::NAN` sentinels
instead of `0.0` (Opus bonus finding). The fields are gated by
`initialised` today, so the `0.0` sentinel never leaked into output —
but a future refactor that read them pre-init would have silently
treated `0.0` as a real price. A `debug_assert!` at the read site makes
the invariant explicit and catches a re-introduction of the bug in
debug builds.
Bit-equivalence with the previous behaviour is preserved
(`reset_allows_clean_reuse` and `batch_equals_streaming` continue to
pass unchanged).
kingchenc
0995f8d66a