Common use of Improved WD Support Clause in Contracts

Improved WD Support. When the user enters an expression or predicate that is possibly ill-defined (such as applying a partial function), the Rodin platform insists that the user demonstrates that this formula is indeed well-defined (e.g., the partial function is applied to an element of its domain) before using it. This verification is implemented by generating a well-definedness (WD) predicate, based on the syntax of the input formula. In previous releases of the Rodin platform, the generation of WD predicates was implemented in a very simple manner, and the generated predicate was usually highly redundant. Moreover, the support by automated tactics for discharging such predicates was not always appropriate. Consequently, many well-definedness subproofs needed to be carried out interactively in a very cumbersome and repetitive manner.