operator ∀ ∃

∀ operand ≡ for each sub-object of the operand

∃ operand ≡ select one sub-object of the operand

Associated by the operator ∀ or ∃, the operand is regarded as a collection, and its first level sub-objects are regarded as elements of a collection.

After any formula solving, there is a collection of combinations of the assigned unknown content operands gotten. We can use the operator ∀ to produce the macro for each, or use the operator ∃ to choose one.