Modify and Logical

[Denis Berthier]

Modify and Logical 

A fact or template F within a logical in the conditions of a rule can be retracted in the conclusion, but if it is retracted, the logical around it is useless. However, it may be useful to allow this presence of "retract", because other conclusions of the same rule may be assertions depending on the same conditions

But, If F is modified in the conclusion, it will indeed be only retracted (unconditionally) and the syntax should probably not allow using "modify" (at least without any warning) when only "retract" will be applied.

I think it should be useful to add some remark about this in the Basic User Manual (under both the "logical" and "modify" entries). It may be useful also to issue a parse-time warning when this situation occurs in a rule.