FA-97553 / Knitting and sewing pattern grading / Member archive

Seam and hem allowance cutter: fold width · case 03

A place-on-fold bodice is cut at double width.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Pieces [name, finished_w, finished_h, on_fold, hemmed]. Cut width = w/2 + sa when cut on the fold (no allowance on the fold), else w + 2*sa. Cut height = h + sa (top) + (hem if hemmed else sa). Fabric area counts the unfolded piece (2*cut width for fold pieces) * cut height, summed and half-up to cm^2. A non-positive finished dimension -> "error: piece". Return [[name, cut_w, cut_h] floats, area].

Why this case matters

Pattern drafting software adds seam and hem allowances and handles place-on-fold pieces.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
fold piece	`[[["front", 43.5, 58.0]], 5046]`	`[[["front", 22.5, 58.0]], 2610]`	Failed

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