(library (tests bignum-to-flonum)
  (export run-tests)
  (import (ikarus) (tests framework))


  (define (run-tests)
    (test-bignum-to-flonum)
    (test-bignum->flonum))



  (define (t x s)
    (let ([fl (format "~a" (exact->inexact x))])
      (unless (string=? s fl)
        (error 'bignum->flonum
          "incorrect result for ~s\n expected ~a, \n      got ~a" x s fl))))
  (define-syntax test*
    (syntax-rules ()
      [(_ name [num str] ...)
       (define-tests name 
         [(lambda (x) (string=? str (number->string x))) (exact->inexact num)]
         ...)]))

  (define (testnum x) 
    (define precision 53)
    ;(assert (bignum? x)) 
    (let ([fl (inexact x)])
      (let ([n (if (> x 0) x (- x))])
        (let ([bits (bitwise-length n)])
          (printf "bits(~s) = ~s\n" n bits)
          (cond
            [(<= bits precision) 
             (unless (= x (exact fl))
               (error #f "should be exactly equal" x fl (exact fl)))]
            [else 
             (let ([hi53 (sra n (- bits precision))]
                   [lo (bitwise-and n (- (sll 1 (- bits precision)) 1))]
                   [breakpoint (sll 1 (- bits precision 1))])
               (assert (= n (+ lo (sll hi53 (- bits precision)))))
               (let ([fl2
                      (cond
                        [(or (< lo breakpoint) 
                             (and (= lo breakpoint) (even? hi53)))
                         (* (inexact hi53) (sll 1 (- bits precision)))]
                        [else
                         (* (inexact (+ hi53 1)) (sll 1 (- bits precision)))])])
                 (let ([fl2 (if (> x 0) fl2 (* fl2 -1))])
                   (printf "x=~s fl=~s\n" x fl)
                   (unless (fl=? fl fl2) 
                     (error #f "should be equal" x fl fl2)))))])))))


  (define (test-pos-neg x)
    (testnum x)
    (testnum (- x)))


  (test* test-bignum-to-flonum
    (1000000000  "1e9")
    (2000000000  "2e9")
    (4000000000  "4e9")
    (-1000000000 "-1e9")
    (-2000000000 "-2e9")
    (-4000000000 "-4e9")
    ( 6000000000   "6e9")
    (12000000000 "1.2e10")
    (25000000000 "2.5e10")
    (50000000000   "5e10")
    (-6000000000  "-6e9")
    (-12000000000 "-1.2e10")
    (-25000000000 "-2.5e10")
    (-50000000000 "-5e10")
    (100000000000 "1e11")
    (200000000000 "2e11")
    (400000000000 "4e11")
    (800000000000 "8e11")
    (-100000000000 "-1e11")
    (-200000000000 "-2e11")
    (-400000000000 "-4e11")
    (-800000000000 "-8e11")
    (#x1FFFFFFFFFFFFF   "9.007199254740991e15")
    (#x3FFFFFFFFFFFFF   "1.8014398509481984e16")
    (#x7FFFFFFFFFFFFF   "3.602879701896397e16")
    (#xFFFFFFFFFFFFFF   "7.205759403792794e16")
    (#x1FFFFFFFFFFFFFF  "1.4411518807585587e17")
    (#x3FFFFFFFFFFFFFF  "2.8823037615171174e17")
    (#x7FFFFFFFFFFFFFF  "5.764607523034235e17")
    (#xFFFFFFFFFFFFFFF  "1.152921504606847e18")
    (#xFFFFFFFFFFFFFFFF "1.8446744073709552e19")
    (1000000000000000000000 "1e21")
    (100000000000000000000000000000 "1e29")
    (100000000000000000000000000000000000000000000000 "1e47")
    (-1000000000000000000000 "-1e21")
    (-100000000000000000000000000000 "-1e29")
    (-100000000000000000000000000000000000000000000000 "-1e47"))
  
  
  (define (test-bignum->flonum)
    (test-pos-neg 34872389478)
    (test-pos-neg 34872389479)
    (test-pos-neg 3487238948347878)
    (test-pos-neg 3487238948347879)
    (test-pos-neg 5487238948347878)
    (test-pos-neg 5487238948347879)
    (test-pos-neg 543877238948347878)
    (test-pos-neg 543877238948347879)
    (test-pos-neg 5438748878948347878)
    (test-pos-neg 5438748878948347879)
    (test-pos-neg 13874887238948347878)
    (test-pos-neg 13874887238948347879)
    (test-pos-neg 543874887238948347878)
    (test-pos-neg 543874887238948347879)
    (test-pos-neg 5433847834874887238948347878)
    (test-pos-neg 5433847834874887238948347879)
    (test-pos-neg 329847892374892374895433847834874887238948347878)
    (test-pos-neg 329847892374892374895433847834874887238948347879)
    (test-pos-neg 
      13407807929942598588139732355608757972494524375225679733981068131349151486565474898751136354405850399729303719974268319295398132445078977825297784408899585)
    (test-pos-neg
      13407807929942598588139732355608757972494524375225679733981068131349151486565474898751136354405850399729303719974268319295398132445078977825297784408899584)
    (test-pos-neg
      13407807929942598588139732355608757972494524375225679733981068131349151486565474898751136354405850399729303719974268319295398132445078977825297784408899586)
    (test-pos-neg
      1340780792994259858813973235560875797249452437522567973398106813134915148656547489875113635440585039972930371997426831929539813244507897782529778440889958413407807929942598588139732355608757972494524375225679733981068131349151486565474898751136354405850399729303719974268319295398132445078977825297784408899584))
    

  
  )