On Thu, Feb 20, 2014 at 2:50 AM, Pascal J. Bourguignon pjb@informatimago.com wrote:
Faré fahree@gmail.com writes:
Subtle bug in ABCL.
What should this form read as? `#5(1 ,@`(2 3))
ECL, LispWorks and fare-quasiquote agree on #(1 2 3 2 3)
Oops, bad copy/paste. The correct answer is #(1 2 3 3 3) indeed as pjb points out, and ECL, LispWorks and fare-quasiquote get it right.
allegro, ccl, clisp, sbcl return the arguably conformant #(1 2 3 2 3 2 3 2 3) abcl, cmucl, gcl, xcl all return the arguably completely buggy #(1 2 3)
#5( anything ) should return a vector of dimension 5 in any case.
That's also my interpretation. allegro, ccl, clisp, sbcl, seem to disagree.
Furthermore,
"If the number of objects supplied before the closing ) is less than the unsigned decimal integer but greater than zero, the last object is used to fill all remaining elements of the vector."so they're all wrong, and expected result should be: #5(1 2 3 3 3)
No, I was wrong in copy/pasting. The result is indeed #(1 2 3 3 3). Mea culpa.
Basically,
`#5(1 ,@`(2 3))should take:
`#(1 ,@`(2 3))which all implementation agree that's read as:
#(1 2 3)and extends the last element to give:
#5(1 2 3 3 3)Now, since the reader macro is #`, we should really apply #` rules, but the only rule for vectors is:
- `#(x1 x2 x3 ... xn) may be interpreted to mean (apply #'vector `(x1 x2 x3 ... xn)).
so one could argue that there's no rule for `#n(…), and therefore it's not a conforming form anyways.
If #n(…) is collapsed to #(…) then the abcl result is correct, as per the above rule.
Maybe it should be an error, then, or demons should be made to fly out of one's nose.
—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org Some cause happiness wherever they go. Others whenever they go.