Pin the interval algebra on the type that already carried it
req:pitch:transposition, implemented as Pitch::transposed. With n the
nominal's normative discriminant and s = nominal.chromatic() + alteration +
12*octave:
nominal' = CmnNominal((n + d).rem_euclid(7))
octave' = octave + (n + d).div_euclid(7)
alteration' = (s + c) - (nominal'.chromatic() + 12*octave')
The diatonic component alone picks the nominal and octave; the alteration
absorbs the residue. C4 + (7, 12) is C5, not C with twelve sharps. C4 + (0, 1)
is C#4, so the editor's sharpen is unchanged. A perfect fifth (4, 7) and a
diminished sixth (5, 7) from C4 give G4 and A-double-flat-4: same sound,
different spelling, which is the whole reason the interval is a pair.
TranspositionInterval moves from graph.rs to pitch.rs. It already existed --
Instrument.transposition has carried it since schema major 2, already codec'd,
already exported -- and it is byte-for-byte the pair this needs. The spec now
declares it once, in Chapter 2 where transposition lives, so the struct sits
where its algebra does. Wire form and codec are untouched.
Its doc claimed it was "ADVISORY until the Chapter 4 tuning catalog pins
interval algebra". That was the P12-K2 false coupling repeated a third time.
The field stays advisory because nothing applies it at the written/sounding
boundary -- for that reason, not for want of algebra, which needs no catalog.
Refusal, never saturation: TransposeRefusal::{NonCmnPosition, AcousticPinned,
OutOfRange}. An AbsoluteHz pitch overrides the tuning system, so transposing
it would move the notehead and leave the sound behind; the mutation that drops
that guard returns Ok(G4 ... AbsoluteHz(261.6)), a notehead reading G4 that
still sounds middle C. TranspositionInterval::inverse is exact precisely
because nothing saturates.
Six tests, four mutations verified: the old alteration-shift semantics, a
clamp in place of the refusal, a truncating `/` in place of div_euclid (which
breaks C4 down a step to B3), and dropping the AbsoluteHz guard.
One process note. The AbsoluteHz mutation appeared to survive on the first
run. It had not: rustfmt had wrapped the matches! across three lines, so the
string replacement silently matched nothing and the test was never challenged.
A mutation that no-ops looks exactly like a test that passes. Mutations now
assert their anchor before applying.
Gate: clippy 0, core 165+5 passed / 0 failed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
parent
357e8b9eeb
commit
27c80a0d83
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@ -60,8 +60,8 @@ use crate::graph::{
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SpannerKind, Staff, StaffBasedContent, StaffBracketKind, StaffExtent, StaffGroup,
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StaffGroupKind, StaffInstance, StaffLineConfiguration, StemDirection, SubBeam,
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TempoMapReference, TextLineDefinition, Tie, TieClass, TimeExtent, TimeSignature,
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TimeSignatureDisplay, Timestamp, TranspositionInterval, Tuplet, TupletRatio, UnpitchedMember,
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ViewDefinition, Voice, VoiceOrigin, Volta,
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TimeSignatureDisplay, Timestamp, Tuplet, TupletRatio, UnpitchedMember, ViewDefinition, Voice,
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VoiceOrigin, Volta,
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};
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use crate::ids::{
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AnalysisLayerId, AnalyticalAnnotationId, BarlineAlignmentGroupId, BeamId, ChordSymbolId,
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@ -76,7 +76,7 @@ use crate::pitch::{
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PositionRegistryId, ReferencePitch, ScalePosition, SpellingAttachment, SpellingDirective,
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SpellingNominal, SpellingPrecedence, SpellingRenderHints, SpellingRule, SpellingRuleSetId,
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SpellingScope, SpellingSource, SpellingSourceKind, StaffGroupKindRegistryId,
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TieClassRegistryId, TuningReference, TuningSystemId, VoiceSelector,
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TieClassRegistryId, TranspositionInterval, TuningReference, TuningSystemId, VoiceSelector,
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};
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use crate::tempo::{Tempo, TempoMap, TempoSegment, TempoShape};
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use crate::time::{
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@ -26,7 +26,8 @@ use crate::ids::{
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TupletId, ViewId, VoiceId,
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};
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use crate::pitch::{
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ForeignFormatId, PitchRange, PitchSpaceId, ReferencePitch, SpellingAttachment, TuningSystemId,
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ForeignFormatId, PitchRange, PitchSpaceId, ReferencePitch, SpellingAttachment,
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TranspositionInterval, TuningSystemId,
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};
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use crate::time::{MeasurePosition, MusicalDuration, TimeAnchor, WallClockDuration};
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@ -1522,18 +1523,6 @@ pub struct ScoreMetadata {
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#[derive(Clone, PartialEq, Eq, Debug, Default)]
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pub struct SoundConfiguration(pub Vec<u8>);
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/// A written-versus-sounding transposition (Chapter 5 §"Instruments";
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/// schema major 2). Structural only: the diatonic and chromatic step
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/// counts of the interval (e.g., B-flat clarinet = -1 diatonic,
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/// -2 chromatic). Semantically ADVISORY until the Chapter 4 tuning
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/// catalog pins interval algebra (the P12-K2 discipline): nothing in
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/// the core resolves it to frequencies or respells through it yet.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub struct TranspositionInterval {
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pub diatonic_steps: i32,
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pub chromatic_steps: i32,
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}
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/// One playable member of an unpitched instrument (Chapter 5
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/// §"Instruments"; schema major 2). `member` is an instrument-scoped
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/// small value (not a 128-bit object id); resolution from
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@ -1568,7 +1557,16 @@ pub struct Instrument {
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pub abbreviation: Option<String>,
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/// Schema major 2 (appended; migration default empty).
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pub sound_config: SoundConfiguration,
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/// Schema major 2 (appended; migration default `None`).
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/// The written-versus-sounding interval of a transposing instrument (a
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/// B-flat clarinet is `-1` diatonic, `-2` chromatic). Schema major 2
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/// (appended; migration default `None`).
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///
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/// Its *action* on a pitch is pinned by [`Pitch::transposed`]
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/// (`req:pitch:transposition`). What is still unimplemented is its
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/// *automatic application* at the written/sounding boundary: nothing here
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/// respells a written part into a sounding one, or resolves either to a
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/// frequency. So the field remains advisory — for that reason, and not,
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/// as this doc once claimed, for want of interval algebra.
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pub transposition: Option<TranspositionInterval>,
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/// Schema major 2 (appended; migration default treble).
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pub default_clef: Clef,
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@ -81,8 +81,8 @@ pub use pitch::{
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PitchSpelling, PositionRegistryId, ReferencePitch, ScalePosition, SpellingAlgorithmId,
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SpellingAttachment, SpellingContext, SpellingDirective, SpellingNominal, SpellingPrecedence,
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SpellingRenderHints, SpellingRule, SpellingRuleSetId, SpellingScope, SpellingSource,
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SpellingSourceKind, StaffGroupKindRegistryId, TieClassRegistryId, TuningReference,
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TuningSystemId, VoiceSelector,
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SpellingSourceKind, StaffGroupKindRegistryId, TieClassRegistryId, TransposeRefusal,
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TranspositionInterval, TuningReference, TuningSystemId, VoiceSelector,
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};
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pub use prepass::{
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@ -114,8 +114,8 @@ pub use graph::{
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SoundConfiguration, SpaceUnit, SpanStyle, Spanner, SpannerKind, Staff, StaffBasedContent,
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StaffBracketKind, StaffExtent, StaffGroup, StaffGroupKind, StaffInstance,
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StaffLineConfiguration, StemDirection, SubBeam, TempoMapReference, TextLineDefinition, Tie,
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TieClass, TimeExtent, TimeSignature, TimeSignatureDisplay, Timestamp, TranspositionInterval,
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Tuplet, TupletRatio, UnpitchedMember, ViewDefinition, Voice, VoiceOrigin, Volta,
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TieClass, TimeExtent, TimeSignature, TimeSignatureDisplay, Timestamp, Tuplet, TupletRatio,
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UnpitchedMember, ViewDefinition, Voice, VoiceOrigin, Volta,
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};
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pub use tempo::{
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@ -180,6 +180,129 @@ impl CmnNominal {
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CmnNominal::B => 11,
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}
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}
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/// The nominal for a diatonic index in `0..7`, the inverse of the type's
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/// normative discriminant (Chapter 2 §"The CmnNominal Type"). Panics
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/// outside the range; callers reduce with `rem_euclid(7)` first.
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fn from_index(index: i32) -> Self {
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match index {
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0 => CmnNominal::C,
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1 => CmnNominal::D,
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2 => CmnNominal::E,
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3 => CmnNominal::F,
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4 => CmnNominal::G,
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5 => CmnNominal::A,
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6 => CmnNominal::B,
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other => unreachable!("diatonic index out of 0..7: {other}"),
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}
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}
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}
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/// A signed interval: the transposition primitive (Chapter 2
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/// §"Transposition and the Interval Type"; schema major 2). Both components
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/// are load-bearing — the diatonic one fixes the spelling (which nominal,
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/// hence which staff line), the chromatic one fixes the sound. Neither
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/// determines the other: an augmented second `(1, 3)` and a minor third
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/// `(2, 3)` sound alike and are written differently.
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///
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/// [`Instrument::transposition`](crate::Instrument) carries one as its
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/// written-versus-sounding interval (a B-flat clarinet is `-1` diatonic, `-2`
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/// chromatic). Its *action* is pinned by [`Pitch::transposed`]; what stays
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/// advisory is its automatic application at the written/sounding boundary,
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/// which nothing in the core performs yet.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub struct TranspositionInterval {
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pub diatonic_steps: i32,
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pub chromatic_steps: i32,
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}
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impl TranspositionInterval {
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/// The interval that undoes this one. Exact, because [`Pitch::transposed`]
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/// never saturates — it refuses instead.
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pub fn inverse(self) -> Self {
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TranspositionInterval {
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diatonic_steps: -self.diatonic_steps,
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chromatic_steps: -self.chromatic_steps,
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}
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}
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}
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/// Why a pitch could not be faithfully transposed (Chapter 2
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/// `req:pitch:transposition`). Each variant is a way a transposition would
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/// otherwise have to lie.
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub enum TransposeRefusal {
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/// The position is not [`PitchSpacePosition::Cmn`], so it has no nominal
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/// for the interval's diatonic component to move.
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NonCmnPosition,
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/// The pitch's [`AcousticRealization::AbsoluteHz`] overrides the tuning
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/// system, so moving the scale position would move the notehead without
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/// moving the sound.
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AcousticPinned,
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/// The resulting `alteration` or `octave` does not fit its `i8` field.
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OutOfRange,
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}
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impl Pitch {
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/// Transposes this pitch by `interval`, per Chapter 2
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/// `req:pitch:transposition`.
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///
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/// With `n` the nominal's normative discriminant and the absolute semitone
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/// `s = nominal.chromatic() + alteration + 12*octave`, transposing by
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/// `{ d, c }` yields
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///
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/// ```text
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/// nominal' = CmnNominal((n + d).rem_euclid(7))
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/// octave' = octave + (n + d).div_euclid(7)
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/// alteration' = (s + c) - (nominal'.chromatic() + 12*octave')
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/// ```
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///
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/// The diatonic component alone selects the nominal and octave; the
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/// alteration absorbs exactly the residue. So `C4 + (7, 12)` is `C5`, not
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/// "C with twelve sharps", and `C4 + (0, 1)` is `C#4`.
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///
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/// Refuses rather than saturating, clamping, or approximating: a
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/// transposition that silently produces a pitch nobody asked for reports
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/// success and destroys the evidence needed to notice.
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pub fn transposed(&self, interval: TranspositionInterval) -> Result<Pitch, TransposeRefusal> {
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if matches!(
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self.acoustic.realization,
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AcousticRealization::AbsoluteHz(_)
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) {
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return Err(TransposeRefusal::AcousticPinned);
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}
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let PitchSpacePosition::Cmn {
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nominal,
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alteration,
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octave,
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} = self.scale_position.position
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else {
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return Err(TransposeRefusal::NonCmnPosition);
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};
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// Widen before arithmetic: the i8 bound is a *result* constraint, not
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// an intermediate one, so an octave that overflows on the way to a
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// value that fits would be a spurious refusal.
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let n = nominal as i32;
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let semitone =
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i32::from(nominal.chromatic()) + i32::from(alteration) + 12 * i32::from(octave);
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let step = n + interval.diatonic_steps;
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let new_nominal = CmnNominal::from_index(step.rem_euclid(7));
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let new_octave = i32::from(octave) + step.div_euclid(7);
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let new_alteration = (semitone + interval.chromatic_steps)
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- (i32::from(new_nominal.chromatic()) + 12 * new_octave);
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let octave = i8::try_from(new_octave).map_err(|_| TransposeRefusal::OutOfRange)?;
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let alteration = i8::try_from(new_alteration).map_err(|_| TransposeRefusal::OutOfRange)?;
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let mut out = self.clone();
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out.scale_position.position = PitchSpacePosition::Cmn {
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nominal: new_nominal,
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alteration,
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octave,
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};
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Ok(out)
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}
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}
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/// A position within a pitch space (Chapter 2 §"Scale Position"). Tagged union
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@ -857,6 +980,145 @@ mod tests {
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assert_eq!(CmnNominal::B.chromatic(), 11);
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}
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fn iv(diatonic_steps: i32, chromatic_steps: i32) -> TranspositionInterval {
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TranspositionInterval {
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diatonic_steps,
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chromatic_steps,
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}
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}
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fn position(p: &Pitch) -> (CmnNominal, i8, i8) {
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match p.scale_position.position {
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PitchSpacePosition::Cmn {
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nominal,
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alteration,
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octave,
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} => (nominal, alteration, octave),
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ref other => panic!("expected a Cmn position, got {other:?}"),
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}
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}
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#[test]
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fn transposing_an_octave_moves_the_octave_not_the_alteration() {
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// The P12-K2 defect, locked: the old alteration-shift produced
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// `C4 alteration 12` — a C with six double-sharps — for this input.
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let up = cmn(CmnNominal::C, 0, 4).transposed(iv(7, 12)).unwrap();
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assert_eq!(position(&up), (CmnNominal::C, 0, 5));
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let down = cmn(CmnNominal::C, 0, 4).transposed(iv(-7, -12)).unwrap();
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assert_eq!(position(&down), (CmnNominal::C, 0, 3));
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}
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#[test]
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fn the_diatonic_component_picks_the_nominal_and_the_alteration_absorbs_the_rest() {
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// A perfect fifth up: C4 -> G4, no accidental.
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let fifth = cmn(CmnNominal::C, 0, 4).transposed(iv(4, 7)).unwrap();
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assert_eq!(position(&fifth), (CmnNominal::G, 0, 4));
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// A *diminished* sixth up sounds the same and is spelled a step away.
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let dim6 = cmn(CmnNominal::C, 0, 4).transposed(iv(5, 7)).unwrap();
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assert_eq!(position(&dim6), (CmnNominal::A, -2, 4));
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// Sharpening: the editor's `transpose_selection(1)` equivalent. This
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// is the one case the frozen operation already got right.
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let sharp = cmn(CmnNominal::C, 0, 4).transposed(iv(0, 1)).unwrap();
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assert_eq!(position(&sharp), (CmnNominal::C, 1, 4));
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}
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|
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#[test]
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fn transposition_crosses_the_octave_boundary_in_both_directions() {
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// B4 up a semitone spelled as a diatonic step: C5, not B#4.
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let up = cmn(CmnNominal::B, 0, 4).transposed(iv(1, 1)).unwrap();
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assert_eq!(position(&up), (CmnNominal::C, 0, 5));
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// C4 down a diatonic step: B3. Euclidean, so the negative index wraps
|
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// to 6 and the octave carries -1.
|
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let down = cmn(CmnNominal::C, 0, 4).transposed(iv(-1, -1)).unwrap();
|
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assert_eq!(position(&down), (CmnNominal::B, 0, 3));
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|
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// B#4 exists and sounds as C5, an octave *below* the C it spells past.
|
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let bsharp = cmn(CmnNominal::B, 1, 4).transposed(iv(0, 0)).unwrap();
|
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assert_eq!(position(&bsharp), (CmnNominal::B, 1, 4));
|
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}
|
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|
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#[test]
|
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fn every_transposition_is_undone_by_its_inverse() {
|
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let start = cmn(CmnNominal::E, -1, 3);
|
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for interval in [iv(4, 7), iv(-2, -3), iv(7, 12), iv(0, 1), iv(5, 7)] {
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let there = start.transposed(interval).unwrap();
|
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let back = there.transposed(interval.inverse()).unwrap();
|
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assert_eq!(
|
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position(&back),
|
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position(&start),
|
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"{interval:?} did not round-trip"
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn a_transposition_refuses_rather_than_saturating() {
|
||||
// The old operation clamped `alteration` at the i8 bound and reported
|
||||
// success. An octave past the i8 bound must refuse instead.
|
||||
let high = cmn(CmnNominal::C, 0, 127);
|
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assert_eq!(
|
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high.transposed(iv(7, 12)),
|
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Err(TransposeRefusal::OutOfRange)
|
||||
);
|
||||
let low = cmn(CmnNominal::C, 0, -128);
|
||||
assert_eq!(
|
||||
low.transposed(iv(-7, -12)),
|
||||
Err(TransposeRefusal::OutOfRange)
|
||||
);
|
||||
|
||||
// An alteration that overflows while the octave is fine.
|
||||
let alt = cmn(CmnNominal::C, 120, 4);
|
||||
assert_eq!(alt.transposed(iv(0, 20)), Err(TransposeRefusal::OutOfRange));
|
||||
|
||||
// Nothing is mutated on refusal — `transposed` is by-value.
|
||||
assert_eq!(position(&high), (CmnNominal::C, 0, 127));
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn a_transposition_refuses_a_non_cmn_position() {
|
||||
let mut p = cmn(CmnNominal::C, 0, 4);
|
||||
p.scale_position.position = PitchSpacePosition::Integer {
|
||||
space_size: 31,
|
||||
index: 7,
|
||||
};
|
||||
assert_eq!(
|
||||
p.transposed(iv(4, 7)),
|
||||
Err(TransposeRefusal::NonCmnPosition)
|
||||
);
|
||||
|
||||
p.scale_position.position = PitchSpacePosition::JiVector {
|
||||
components: vec![1, 0, -1],
|
||||
};
|
||||
assert_eq!(
|
||||
p.transposed(iv(0, 0)),
|
||||
Err(TransposeRefusal::NonCmnPosition)
|
||||
);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn a_transposition_refuses_a_pitch_pinned_to_a_frequency() {
|
||||
// AbsoluteHz overrides the tuning system: moving the scale position
|
||||
// would move the notehead and leave the sound where it was.
|
||||
let mut p = cmn(CmnNominal::C, 0, 4);
|
||||
p.acoustic.realization = AcousticRealization::absolute_hz(261.6).unwrap();
|
||||
assert_eq!(
|
||||
p.transposed(iv(4, 7)),
|
||||
Err(TransposeRefusal::AcousticPinned)
|
||||
);
|
||||
|
||||
// A cents offset is relative to whatever the tuning produces for the
|
||||
// *new* position, so it transposes and survives.
|
||||
let mut q = cmn(CmnNominal::C, 0, 4);
|
||||
q.acoustic.realization = AcousticRealization::cents_offset(-13.7).unwrap();
|
||||
let moved = q.transposed(iv(4, 7)).unwrap();
|
||||
assert_eq!(position(&moved), (CmnNominal::G, 0, 4));
|
||||
assert_eq!(moved.acoustic.realization, q.acoustic.realization);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn pitch_range_contains_is_advisory_and_frame_aware() {
|
||||
let range = PitchRange {
|
||||
|
|
|
|||
Loading…
Reference in New Issue