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at 2024-03-10T12:52:20-07:00

Use builtin constants to get the range of valid exponents.

Instead of hard-wiring the min and max exponents, use
`vm:single-float-normal-expenent-min`, and
`vm:single-float-normal-exponent-max` to get the exponents.  These
need to be adjusted by `vm:single-float-bias` and
`vm:single-float-digits` as appropriate to go the actual signed
exponents ranges.   We use analogous values for double-floats.

@@ -1845,12 +1845,22 @@ the end of the stream."
          (multiple-value-bind (log2-low log2-high)
              (ecase float-format
                ((short-float single-float)
 -               ;; Single-float exponents range is -149 to 127
 -               (values (* 2 -149) (* 2 127)))
 +               ;; Single-float exponents range is -149 to 127, but we
 +               ;; don't need to be super-accurate since we're
 +               ;; multiplying the values by 2.
 +               (values (* 2 (- vm:single-float-normal-exponent-min
 +                               vm:single-float-bias
 +                               vm:single-float-digits))
 +                       (* 2 (- vm:single-float-normal-exponent-max
 +                               vm:single-float-bias))))
                ((double-float long-float
                               #+double-double kernel:double-double-float)
 -               ;; Double-float exponent range is -1074 to -1023
 -               (values (* 2 -1074) (* 2 1023))))
 +               (values (* 2 (- vm:double-float-normal-exponent-min
 +                               vm:double-float-bias
 +                               vm:double-float-digits))
 +                       (* 2 (- vm:double-float-normal-exponent-max
 +                               vm:double-float-bias)))))
 +          ;; Double-float exponent range is -1074 to -1023
            (unless (< log2-low log2-num log2-high)
              ;; The number is definitely too large or too small to fit.
              ;; Signal an error.

Raymond Toy pushed to branch issue-274-make-float-of-huge-numbers at cmucl / cmucl

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