FA-80864 / Music interval and transposition theory / Member archive

Spelled pitch to MIDI key number: double sharp glyph not consumed · case 04

Any spelling with an x double sharp (Fx4, Cx-1) is rejected as malformed.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input a spelled pitch string: uppercase letter A-G, any run of accidentals (# = +1, b = -1, x = +2), then a signed integer octave where C4 = 60 and C-1 = 0. Return the MIDI key number, or None for malformed text or results outside 0..127.

Why this case matters

Pitch spelling and interval arithmetic decide the notes that notation, transposition and analysis tools display or play.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
oracle 6	`null`	`2`	Failed

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