Edit history: 2004-07-20, Version 1 by Bruno Haible
Status: For CLiki consideration
- Problem Description:
- Is (loop with x of-type nil do (return x)) required to construct and return an "appropriate default value" for type NIL?
- Proposal (LOOP-WITH-NIL:???):
- Test case:
- Current practice:
- Cost to Implementors:
- Cost to Users:
- Cost of Non-Adoption:
- Bruno Haible says: In (LOOP WITH var OF-TYPE typespec ...) the typespec can be an arbitrary type specifier, even one that is a non-recognizable empty type, e.g. (AND (SATISFIES NULL) (SATISFIES INTEGERP)). Therefore the macro expander has to be prepared to choose an arbitrary initialization value and to extend the variable's type:
(LOOP WITH var OF-TYPE (OR typespec (EQL default)) = default ...)I'm not sure this needs to be written explicitly.