FA-97739 / Knitting and sewing pattern grading / Member archive

Knitting needle size converter: half-size notation · case 04

US "10 1/2" is not recognized.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Table US->mm: 0 2.0, 1 2.25, 2 2.75, 3 3.25, 4 3.5, 5 3.75, 6 4.0, 7 4.5, 8 5.0, 9 5.5, 10 6.0, 10.5 6.5, 11 8.0, 13 9.0, 15 10.0. "us->mm": trim, "10 1/2" means "10.5", exact match or "error: size". "mm->us": nearest size within 0.5 mm inclusive, ties to the larger mm, else "error: size". Other directions -> "error: direction".

Why this case matters

Patterns list needle sizes in US or metric and knitters convert between them.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: half-size notation	`"error: size"`	`6.5`	Failed

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