Constrained generation and fuzzy formulas

In contrast to orderly generation, constrained generation does not use a fixed order of generation, rather it is controlled by the constraints. The strategy for adding bonds 

As the generation is formula-based, the molecular formula is required. A generalization also allows input of a fuzzy molecular formula, i.e. with intervals for multiplicities  

13 Definition (Fuzzy molecular formula) Let denote a set of chemical elements and 

In order to keep the input as flexible as possible, we allow the input of several fuzzy formulas, each of them accompanied by its own restrictions. 

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