Not really outright bugs, but these responses are less than awesome:
$ guile -c '(write (logbit? (ash 1 100) 123))'
ERROR: Value out of range 0 to 18446744073709551615:
1267650600228229401496703205376
$ guile -c '(write (ash 0 (ash 1 100)))'
ERROR: Value out of range -9223372036854775808 to 9223372036854775807:
1267650600228229401496703205376
$ guile -c '(write (ash 123 (ash -1 100)))'
ERROR: Value out of range -9223372036854775808 to 9223372036854775807:
-1267650600228229401496703205376
In all three cases, the theoretically-correct result of the expression
is not only representable but easily computed. The functions could be
improved to avoid failing in these cases, by adding logic amounting to:
(define (better-logbit? b v)
(if (>= b (integer-length v)) (< v 0) (logbit? b v)))
(define (better-ash v s)
(cond
((= v 0) 0)
((<= s (- (integer-length v))) (if (< v 0) -1 0))
(else (ash v s))))
-zefram
