Issue LOOP-WITH-NIL
Issue: LOOP-WITH-NIL
Forum: Editorial
References: LOOP
Category: CLARIFICATION/CHANGE
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:???):
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- Test case:
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- Rationale:
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- Current practice:
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- Cost to Implementors:
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- Cost to Users:
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- Cost of Non-Adoption:
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- Benefits:
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- Aesthetics:
- Discussion:
- 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.
This page is linked from: Proposed ANSI Revisions and Clarifications
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