FA-97818 / Knitting and sewing pattern grading / Member archive

Circle skirt drafter: fabric span hem · case 03

The fabric width check ignores the hem allowance and the skirt cannot be cut in one piece.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

kind full/half/quarter covers fraction 1, 1/2, 1/4 of a circle (else "error: kind"). Waist radius r = (waist+ease)/(2*pi*fraction); cut radius = r - sa (seam extends into the waist hole). Hem circumference = 2*pi*fraction*(r + length). Fabric span needed = 2*(cut_r + length + hem) for full and half, (cut_r + length + hem) for quarter. Return floats rounded to 1 decimal: [r, cut_r, hem_circumference, span].

Why this case matters

Circle skirt drafting converts waist size into a radius and checks the fabric width needed.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
full circle	`[11.5, 10.0, 417.6, 129.9]`	`[11.5, 10.0, 417.6, 133.9]`	Failed

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