WSCL issue: sequence-definition #50
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| N/A (Test cases are difficult to provide, because conformating |
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(subtypep 'sequence '(or vector list)) could return T NIL or NIL NIL on an implementation conforming to this proposal, but NIL T would indicate nonconformance.
Also: "conforming"
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I'm not sure about this.. For a conforming implementation, we do need (subtypep '(or vector list) 'sequence) to return T T. However, the point of this issue is to give such an implementation the freedom to have something else in the type sequence.
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You read the arguments backwards. I'm saying you can test whether sequence is a subtype of (or vector list), not the other way around. If any non-list non-vector sequences are possible, sequence is not a subtype of (or vector list).
Of course I suppose this proposal doesn't necessarily require implementations to have non-vector non-list sequences, so maybe the subtype is inappropriate after all. Considered that way, having test cases at all would be inappropriate, since it's just making the standard more flexible without requiring any implementation to make any changes whatsoever.
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I am still confused. Why would (subtypep 'sequence '(or vector list))'s returning NIL T indicate nonconformance to this proposal? This proposal aims to provide the freedom for an implementation to have sequence to possibly have things more than just vectors and lists.
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A value of NIL, T or NIL, NIL indicates the implementation does not conform to the current [b].
For this issue, the test cases would not indicate conformance or non-conformance, but indicate whether LIST and VECTOR are exhaustive for the typespace of SEQUENCE. Supporting extensible sequences would require returning NIL, T, I would think.
Test Cases:
(defun one ()
(subtypep 'sequence '(or vector list)))
(one) ; => T, T
Rationale:
This is a plain contradiction in dpANS.
Current Practice:
ABCL 1.9.3-dev-fasl43
(one) ; => NIL, NIL
SBCL 2.4.1
(one) ; => NIL, T
CLASP cclasp-boehmprecise-2.5.0-247-g4b148619f-g85ffab47-cst
(one) ; => T, T
ECL 23.9.9-f477a3ef
(one) ; => T, T
CMU 2024-03-10 18:28:32 (21E Unicode)
(one) ; => T, T
CCL 1.12-f98
(one) ; => T, T
In the draft ANSI Common Lisp specification, the description of the system class SEQUENCE conflicts with the description of the Sequence Concepts. This issue fixes the conflict.