Martino FerrariandClaude Opus 4.6
e337c6a60c
A range straddling zero never lands *on* zero: the walk starts at `ceil(min / stride) * stride`, which is not representable whenever the stride is not a power of two -- 0.1 and 0.2 are the everyday ones -- so the tick that means zero arrives a few ULP off and `format_si` labels it from six prefixes down. `[-1, 1]` read `-1 -500m -139a 500m 1`. Deriving the tick by multiplication rather than accumulation does not help, because the error is already in the first term. Every tick is an integer multiple of the stride, so the smallest magnitude a non-zero tick can have is the stride itself, while the residue is a few ULP of the range -- ten orders of magnitude apart. Anything inside a millionth of the stride is therefore the origin and nothing else. It is stored as exactly `0.0` rather than merely labelled so: `Axis::refresh()` re-formats a time axis from `tick.value`, where the same residue reads `3.19e-13ms`. The walk variable is left alone, since `minor_index_is_major` counts indices from `first_major` and both operands have to stay on the walk's own grid. The two narrow-y-title cases were calibrated on the defect -- the bogus `-55.5a` was a six-character label, and its width is what spent the chrome allowance and made the titled and untitled frames comparable. They are re-seated on a milli-scale range, whose `-200m` is wide for a real reason, and the zero-width strip the frame comparison depends on is now asserted rather than assumed. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>