287 lines
10 KiB
Scheme
287 lines
10 KiB
Scheme
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;; Copyright 2010 the V8 project authors. All rights reserved.
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;; Redistribution and use in source and binary forms, with or without
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;; modification, are permitted provided that the following conditions are
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;; met:
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;;
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;; * Redistributions of source code must retain the above copyright
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;; notice, this list of conditions and the following disclaimer.
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;; * Redistributions in binary form must reproduce the above
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;; copyright notice, this list of conditions and the following
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;; disclaimer in the documentation and/or other materials provided
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;; with the distribution.
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;; * Neither the name of Google Inc. nor the names of its
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;; contributors may be used to endorse or promote products derived
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;; from this software without specific prior written permission.
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;;
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;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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;; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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;; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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;; LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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;; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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;; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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;; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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;; This is a Scheme script for the Bigloo compiler. Bigloo must be compiled with
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;; support for bignums. The compilation of the script can be done as follows:
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;; bigloo -static-bigloo -o generate-ten-powers generate-ten-powers.scm
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;;
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;; Generate approximations of 10^k.
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(module gen-ten-powers
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(static (class Cached-Fast
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v::bignum
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e::bint
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exact?::bool))
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(main my-main))
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;;----------------bignum shifts -----------------------------------------------
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(define (bit-lshbx::bignum x::bignum by::bint)
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(if (<fx by 0)
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#z0
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(*bx x (exptbx #z2 (fixnum->bignum by)))))
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(define (bit-rshbx::bignum x::bignum by::bint)
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(if (<fx by 0)
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#z0
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(/bx x (exptbx #z2 (fixnum->bignum by)))))
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;;----------------the actual power generation -------------------------------
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;; e should be an indication. it might be too small.
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(define (round-n-cut n e nb-bits)
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(define max-container (- (bit-lshbx #z1 nb-bits) 1))
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(define (round n)
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(case *round*
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((down) n)
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((up)
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(+bx n
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;; with the -1 it will only round up if the cut off part is
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;; non-zero
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(-bx (bit-lshbx #z1
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(-fx (+fx e nb-bits) 1))
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#z1)))
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((round)
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(+bx n
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(bit-lshbx #z1
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(-fx (+fx e nb-bits) 2))))))
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(let* ((shift (-fx (+fx e nb-bits) 1))
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(cut (bit-rshbx (round n) shift))
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(exact? (=bx n (bit-lshbx cut shift))))
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(if (<=bx cut max-container)
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(values cut e exact?)
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(round-n-cut n (+fx e 1) nb-bits))))
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(define (rounded-/bx x y)
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(case *round*
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((down) (/bx x y))
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((up) (+bx (/bx x y) #z1))
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((round) (let ((tmp (/bx (*bx #z2 x) y)))
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(if (zerobx? (remainderbx tmp #z2))
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(/bx tmp #z2)
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(+bx (/bx tmp #z2) #z1))))))
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(define (generate-powers from to mantissa-size)
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(let* ((nb-bits mantissa-size)
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(offset (- from))
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(nb-elements (+ (- from) to 1))
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(vec (make-vector nb-elements))
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(max-container (- (bit-lshbx #z1 nb-bits) 1)))
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;; the negative ones. 10^-1, 10^-2, etc.
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;; We already know, that we can't be exact, so exact? will always be #f.
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;; Basically we will have a ten^i that we will *10 at each iteration. We
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;; want to create the matissa of 1/ten^i. However the mantissa must be
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;; normalized (start with a 1). -> we have to shift the number.
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;; We shift by multiplying with two^e. -> We encode two^e*(1/ten^i) ==
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;; two^e/ten^i.
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(let loop ((i 1)
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(ten^i #z10)
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(two^e #z1)
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(e 0))
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(unless (< (- i) from)
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(if (>bx (/bx (*bx #z2 two^e) ten^i) max-container)
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;; another shift would make the number too big. We are
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;; hence normalized now.
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(begin
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(vector-set! vec (-fx offset i)
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(instantiate::Cached-Fast
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(v (rounded-/bx two^e ten^i))
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(e (negfx e))
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(exact? #f)))
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(loop (+fx i 1) (*bx ten^i #z10) two^e e))
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(loop i ten^i (bit-lshbx two^e 1) (+fx e 1)))))
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;; the positive ones 10^0, 10^1, etc.
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;; start with 1.0. mantissa: 10...0 (1 followed by nb-bits-1 bits)
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;; -> e = -(nb-bits-1)
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;; exact? is true when the container can still hold the complete 10^i
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(let loop ((i 0)
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(n (bit-lshbx #z1 (-fx nb-bits 1)))
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(e (-fx 1 nb-bits)))
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(when (<= i to)
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(receive (cut e exact?)
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(round-n-cut n e nb-bits)
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(vector-set! vec (+fx i offset)
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(instantiate::Cached-Fast
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(v cut)
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(e e)
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(exact? exact?)))
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(loop (+fx i 1) (*bx n #z10) e))))
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vec))
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(define (print-c powers from to struct-type
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cache-name max-distance-name offset-name macro64)
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(define (display-power power k)
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(with-access::Cached-Fast power (v e exact?)
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(let ((tmp-p (open-output-string)))
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;; really hackish way of getting the digits
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(display (format "~x" v) tmp-p)
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(let ((str (close-output-port tmp-p)))
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(printf " {~a(0x~a, ~a), ~a, ~a},\n"
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macro64
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(substring str 0 8)
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(substring str 8 16)
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e
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k)))))
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(define (print-powers-reduced n)
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(print "static const " struct-type " " cache-name
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"(" n ")"
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"[] = {")
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(let loop ((i 0)
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(nb-elements 0)
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(last-e 0)
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(max-distance 0))
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(cond
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((>= i (vector-length powers))
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(print " };")
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(print "static const int " max-distance-name "(" n ") = "
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max-distance ";")
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(print "// nb elements (" n "): " nb-elements))
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(else
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(let* ((power (vector-ref powers i))
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(e (Cached-Fast-e power)))
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(display-power power (+ i from))
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(loop (+ i n)
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(+ nb-elements 1)
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e
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(cond
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((=fx i 0) max-distance)
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((> (- e last-e) max-distance) (- e last-e))
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(else max-distance))))))))
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(print "// Copyright 2010 the V8 project authors. All rights reserved.")
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(print "// ------------ GENERATED FILE ----------------")
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(print "// command used:")
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(print "// "
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(apply string-append (map (lambda (str)
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(string-append " " str))
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*main-args*))
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" // NOLINT")
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(print)
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(print
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"// This file is intended to be included inside another .h or .cc files\n"
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"// with the following defines set:\n"
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"// GRISU_CACHE_STRUCT: should expand to the name of a struct that will\n"
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"// hold the cached powers of ten. Each entry will hold a 64-bit\n"
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"// significand, a 16-bit signed binary exponent, and a 16-bit\n"
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"// signed decimal exponent. Each entry will be constructed as follows:\n"
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"// { significand, binary_exponent, decimal_exponent }.\n"
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"// GRISU_CACHE_NAME(i): generates the name for the different caches.\n"
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"// The parameter i will be a number in the range 1-20. A cache will\n"
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"// hold every i'th element of a full cache. GRISU_CACHE_NAME(1) will\n"
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"// thus hold all elements. The higher i the fewer elements it has.\n"
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"// Ideally the user should only reference one cache and let the\n"
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"// compiler remove the unused ones.\n"
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"// GRISU_CACHE_MAX_DISTANCE(i): generates the name for the maximum\n"
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"// binary exponent distance between all elements of a given cache.\n"
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"// GRISU_CACHE_OFFSET: is used as variable name for the decimal\n"
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"// exponent offset. It is equal to -cache[0].decimal_exponent.\n"
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"// GRISU_UINT64_C: used to construct 64-bit values in a platform\n"
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"// independent way. In order to encode 0x123456789ABCDEF0 the macro\n"
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"// will be invoked as follows: GRISU_UINT64_C(0x12345678,9ABCDEF0).\n")
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(print)
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(print-powers-reduced 1)
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(print-powers-reduced 2)
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(print-powers-reduced 3)
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(print-powers-reduced 4)
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(print-powers-reduced 5)
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(print-powers-reduced 6)
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(print-powers-reduced 7)
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(print-powers-reduced 8)
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(print-powers-reduced 9)
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(print-powers-reduced 10)
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(print-powers-reduced 11)
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(print-powers-reduced 12)
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(print-powers-reduced 13)
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(print-powers-reduced 14)
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(print-powers-reduced 15)
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(print-powers-reduced 16)
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(print-powers-reduced 17)
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(print-powers-reduced 18)
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(print-powers-reduced 19)
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(print-powers-reduced 20)
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(print "static const int GRISU_CACHE_OFFSET = " (- from) ";"))
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;;----------------main --------------------------------------------------------
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(define *main-args* #f)
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(define *mantissa-size* #f)
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(define *dest* #f)
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(define *round* #f)
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(define *from* #f)
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(define *to* #f)
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(define (my-main args)
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(set! *main-args* args)
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(args-parse (cdr args)
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(section "Help")
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(("?") (args-parse-usage #f))
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((("-h" "--help") (help "?, -h, --help" "This help message"))
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(args-parse-usage #f))
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(section "Misc")
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(("-o" ?file (help "The output file"))
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(set! *dest* file))
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(("--mantissa-size" ?size (help "Container-size in bits"))
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(set! *mantissa-size* (string->number size)))
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(("--round" ?direction (help "Round bignums (down, round or up)"))
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(set! *round* (string->symbol direction)))
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(("--from" ?from (help "start at 10^from"))
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(set! *from* (string->number from)))
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(("--to" ?to (help "go up to 10^to"))
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(set! *to* (string->number to)))
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(else
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(print "Illegal argument `" else "'. Usage:")
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(args-parse-usage #f)))
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(when (not *from*)
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(error "generate-ten-powers"
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"Missing from"
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#f))
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(when (not *to*)
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(error "generate-ten-powers"
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"Missing to"
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#f))
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(when (not *mantissa-size*)
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(error "generate-ten-powers"
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"Missing mantissa size"
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#f))
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(when (not (memv *round* '(up down round)))
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(error "generate-ten-powers"
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"Missing round-method"
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*round*))
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(let ((dividers (generate-powers *from* *to* *mantissa-size*))
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(p (if (not *dest*)
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(current-output-port)
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(open-output-file *dest*))))
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(unwind-protect
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(with-output-to-port p
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(lambda ()
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(print-c dividers *from* *to*
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"GRISU_CACHE_STRUCT" "GRISU_CACHE_NAME"
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"GRISU_CACHE_MAX_DISTANCE" "GRISU_CACHE_OFFSET"
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"GRISU_UINT64_C"
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)))
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(if *dest*
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(close-output-port p)))))
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