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@@ -1833,25 +1833,31 @@ the end of the stream." |
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1833
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1833
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;; super accurate with the limits. The rest of the code will handle
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1834
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1834
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;; it correctly, even if we're too small or too large.
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1835
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1835
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(unless (zerop number)
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1836
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- (let ((log2-num (+ (kernel::log2 (float (/ number divisor) 1d0))
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1837
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- (* exponent #.(kernel::log2 10d0)))))
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1838
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- (multiple-value-bind (log2-low log2-high)
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1839
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- (ecase float-format
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1840
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- ((short-float single-float)
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1841
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- ;; Single-float exponents range is -149 to 127
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1842
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- (values (* 2 -149) (* 2 127)))
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1843
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- ((double-float long-float
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1844
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- #+double-double kernel:double-double-float)
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1845
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- ;; Double-float exponent range is -1074 to -1023
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1846
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- (values (* 2 -1074) (* 2 1023))))
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1847
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- (when (< log2-num log2-low)
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1848
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- ;; If the number is too small, just return 0.
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1849
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- (return-from make-float-aux (coerce 0 float-format)))
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1836
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+ (flet ((fast-log2 (n)
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1837
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+ ;; For an integer, the integer-length is close enough to
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1838
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+ ;; the log2 of the number.
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1839
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+ (integer-length n)))
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1840
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+ ;; log2(x) = exponent*log2(10) + log2(number)-log2(divisor)
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1841
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+ (let ((log2-num (+ (* exponent #.(kernel::log2 10d0))
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1842
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+ (fast-log2 number)
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1843
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+ (- (fast-log2 divisor)))))
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1844
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+ (multiple-value-bind (log2-low log2-high)
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1845
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+ (ecase float-format
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1846
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+ ((short-float single-float)
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1847
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+ ;; Single-float exponents range is -149 to 127
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1848
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+ (values (* 2 -149) (* 2 127)))
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1849
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+ ((double-float long-float
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1850
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+ #+double-double kernel:double-double-float)
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1851
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+ ;; Double-float exponent range is -1074 to -1023
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1852
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+ (values (* 2 -1074) (* 2 1023))))
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1853
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+ (when (< log2-num log2-low)
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1854
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+ ;; If the number is too small, just return 0.
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1855
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+ (return-from make-float-aux (coerce 0 float-format)))
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1850
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1856
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1851
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- (when (> log2-num log2-high)
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1852
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- ;; The numbe is definitely too large to fit. Signal an error.
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1853
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- (%reader-error stream _"Number not representable as a ~S: ~S"
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1854
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- float-format (read-buffer-to-string))))))
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1857
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+ (when (> log2-num log2-high)
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1858
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+ ;; The numbe is definitely too large to fit. Signal an error.
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1859
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+ (%reader-error stream _"Number not representable as a ~S: ~S"
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1860
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+ float-format (read-buffer-to-string)))))))
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1855
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1861
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1856
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1862
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;; Otherwise the number might fit, so we carefully compute the result
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1857
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1863
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(handler-case
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