A conforming implementation shall adhere to the requirements outlined in this section.
A conforming implementation shall accept all features (including deprecated features) of the language specified in this standard, with the meanings defined in this standard.
A conforming implementation shall not require the inclusion of substitute or additional language elements in code in order to accomplish a feature of the language that is specified in this standard.
A conforming implementation shall be accompanied by a document that provides a definition of all implementation-defined aspects of the language defined by this specification.
In addition, a conforming implementation is encouraged (but not required) to document items in this standard that are identified as implementation-dependent, although in some cases such documentation might simply identify the item as “undefined.”
A conforming implementation shall be accompanied by a document that separately describes any features accepted by the implementation that are not specified in this standard, but that do not cause any ambiguity or contradiction when added to the language standard. Such extensions shall be described as being “extensions to Common Lisp as specified by ANSI «standard number».”
A conforming implementation shall treat exceptional situations in a manner consistent with this specification.
If more than one passage in this specification appears to apply to the same situation but in conflicting ways, the passage that appears to describe the situation in the most specific way (not necessarily the passage that provides the most constrained kind of error detection) takes precedence.
in Exceptional Situations
Suppose that function foo is a member of a set S of functions that
operate on numbers. Suppose that one passage states that an error must be
signaled if any function in S is ever given an argument of 17.
Suppose that an apparently conflicting passage states that the consequences
are undefined if foo receives an argument of 17. Then the second passage
(the one specifically about foo) would dominate because the description of
the situational context is the most specific, and it would not be required that
foo signal an error on an argument of 17 even though other functions in
the set S would be required to do so.
A conforming implementation shall produce a conformance statement as a consequence of using the implementation, or that statement shall be included in the accompanying documentation. If the implementation conforms in all respects with this standard, the conformance statement shall be
If the implementation conforms with some but not all of the requirements of this standard, then the conformance statement shall be