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0|1|2|3|4|5|6|7|8|9No [char-class] — enumerate explicitlyvs Programming RegexFormal RE✨ Emoji Combos

Programming regex: [0-9]. Formal RE has no range syntax — enumerate every member via alternation. Σ represents "any character" but there's no range notation.

✓ Accepts
0159
✗ Rejects
ε10a00
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