(import scheme)
(import (chicken base))
(import (chicken bitwise))
(import (chicken foreign))
(import (srfi 4))

(define double->uint64
  (foreign-lambda* unsigned-integer64 ((double d))
    "uint64_t dest; memcpy(&dest, &d, sizeof(d)); C_return(dest);"))

(define (uint64->u8vector-big i)
  (u8vector (bitwise-and (arithmetic-shift i -56) #xff)
            (bitwise-and (arithmetic-shift i -48) #xff)
            (bitwise-and (arithmetic-shift i -40) #xff)
            (bitwise-and (arithmetic-shift i -32) #xff)
            (bitwise-and (arithmetic-shift i -24) #xff)
            (bitwise-and (arithmetic-shift i -16) #xff)
            (bitwise-and (arithmetic-shift i -8) #xff)
            (bitwise-and i #xff)))

(for-each
 (lambda (double)
   (let* ((integer64 (double->uint64 double))
          (fraction (bitwise-and integer64 #xfffffffffffff))
          (exponent (bitwise-and (arithmetic-shift integer64 -52) #x7ff))
          (sign (if (negative? double) '- '+))
          (binary (uint64->u8vector-big integer64)))
     (write (list double (u8vector->list binary) sign exponent fraction))
     (newline)))
 (list (atan -1) (atan 1) (expt 2.0 64) (- (expt 2.0 64))))

from math import atan
import struct

for double in [atan(-1), atan(1), 2.0**64, -2.0**64]:
    binary = struct.pack('>d', double)
    integer64 = int.from_bytes(binary, 'big')
    fraction = integer64 & 0xfffffffffffff
    exponent = (integer64 >> 52) & 0x7ff
    sign = '-' if double < 0 else '+'
    print([double, list(binary), sign, exponent, fraction])

; ; csc tmp/test.scm && tmp/test
(-0.785398163397448 (191 233 33 251 84 68 45 24) - 1022 2570638124657944)
(0.785398163397448 (63 233 33 251 84 68 45 24) + 1022 2570638124657944)
(1.84467440737096e+19 (67 240 0 0 0 0 0 0) + 1087 0)
(-1.84467440737096e+19 (195 240 0 0 0 0 0 0) - 1087 0)
; ; python tmp/test.py          
[-0.7853981633974483, [191, 233, 33, 251, 84, 68, 45, 24], '-', 1022, 2570638124657944]
[0.7853981633974483, [63, 233, 33, 251, 84, 68, 45, 24], '+', 1022, 2570638124657944]
[1.8446744073709552e+19, [67, 240, 0, 0, 0, 0, 0, 0], '+', 1087, 0]
[-1.8446744073709552e+19, [195, 240, 0, 0, 0, 0, 0, 0], '-', 1087, 0]