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Weak type resolution: plus sign between numbers · case 05

A plus between Arabic numbers joins them, or European pairs split.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input [classes of one isolating run sequence, sos]. W1 NSM takes the previous type (sos at start; ON after LRI/RLI/FSI/PDI). W2 EN after the last strong AL becomes AN. W3 AL->R. W4 a single ES between EN and EN -> EN; a single CS between two numbers of the same type takes that type. W5 a run of ET adjacent to EN -> EN. W6 remaining ES/ET/CS -> ON. W7 EN whose last strong (sos at start) is L -> L. Return resolved classes.

Why this case matters

Mixed right-to-left and left-to-right text must resolve levels and visual order exactly, or words, numbers and carets land in the wrong place.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: plus sign between numbers	`["L", "ON", "R", "R", "ON", "ON", "AN", "EN", "AN"]`	`["L", "ON", "R", "R", "ON", "ON", "AN", "ON", "AN"]`	Failed

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