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ISO 10646 Codification for compound kind
It already handle even the three characters and other special compounds. I'm reporting that here:
Smbl Code p. Name in ISO 10646 Cardinality Label 吅 2FF0 IDC LEFT TO RIGHT IDC2 A 吕 2FF1 IDC ABOVE TO BELOW IDC2 B 罒 2FF2 IDC LEFT TO MIDDLE AND RIGHT IDC3 K 目 2FF3 IDC ABOVE TO MIDDLE AND BELOW IDC3 L 回 2FF4 IDC FULL SURROUND IDC2 I 冂 2FF5 IDC SURROUND FROM ABOVE IDC2 F 凵 2FF6 IDC SURROUND FROM BELOW IDC2 G 匚 2FF7 IDC SURROUND FROM LEFT IDC2 H 厂 2FF8 IDC SURROUND FROM UPPER LEFT IDC2 D 勹 2FF9 IDC SURROUND FROM UPPER RIGHT IDC2 C 匕 2FFA IDC SURROUND FROM LOWER LEFT IDC2 E . 2FFB IDC OVERLAID IDC2 J --- Some more code taken from the one in use at Chinese Characters Decomposition 一 Graphical primitive, non composition (second character is always *) 咒 Vertical composition, the top part being a repetition. 弼 Horizontal composition of three, the third being the repetition of the first. 品 Repetition of three. 叕 Repetition of four. 冖 Vertical composition, separated by "冖". ? Unclear, seems compound but ...