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(car-nil-legal t)

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This is a joke only afficionados of Portable Standard Lisp will understand.
This commit is contained in:
Simon Brooke 2019-08-17 11:02:25 +01:00
parent dbab7651a3
commit bf83fd3d91
1 changed files with 12 additions and 6 deletions
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18
src/beowulf/eval.clj
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@ -27,19 +27,25 @@
(if (or (symbol? x) (number? x)) 'T NIL))
(defn CAR
"Return the item indicated by the first pointer of a pair. NIL is treated
specially: the CAR of NIL is NIL."
[x]
(if
(instance? beowulf.cons_cell.ConsCell x)
(.CAR x)
(cond
(= x NIL) NIL
(instance? beowulf.cons_cell.ConsCell x) (.CAR x)
:else
(throw
(Exception.
(str "Cannot take CAR of `" x "` (" (.getName (.getClass x)) ")")))))
(defn CDR
"Return the item indicated by the second pointer of a pair. NIL is treated
specially: the CDR of NIL is NIL."
[x]
(if
(instance? beowulf.cons_cell.ConsCell x)
(.CDR x)
(cond
(= x NIL) NIL
(instance? beowulf.cons_cell.ConsCell x) (.CDR x)
:else
(throw
(Exception.
(str "Cannot take CDR of `" x "` (" (.getName (.getClass x)) ")")))))