Macro Cthreering[9]

This macro typesets the cyclopropane ring. The aromatic cyclopropenyl cation is drawn with a circle enclosing a plus sign inside the ring. The ring positions to which R1, R2, and R3 are attached are designated as position 1, 2, and 3, respectively:

$\displaystyle \threering$$R1$$R2$$R3$$R4$$R5$$R6$SQQ   $\displaystyle \threering$$R1$$R2$$R3$QQQSQC

Arguments 1–6:
An argument of ``Q'' causes no action. All other argument values are used as the respective substituent formulas R1, R2, R3, R4, R5, and R6. The bond line to R2 is straight if the circle is in the ring or if there is no second substituent at position 2, and slanted otherwise.
Argument 7:
An argument of ``D'' typesets a second bond between ring positions 1 and 3. No action is taken for any other value of the argument.
Argument 8:
An argument of ``Q'' causes no action. All other argument values cause an outside double bond to be drawn from ring position 2, and the argument itself to be put at the end of the double bond as the substituent formula.
Argument 9:
An argument of ``C'' typesets a circle enclosing a plus sign inside the ring. All other argument values cause no action.