Stat overflow

[jmid]

This fixes a rare overflow in the histogram labels (and simplifies a couple of other things).

Before (notice the negative labels on the last bucket):

utop # #require "qcheck";;
utop # open QCheck;;
utop # let t = Test.make ~count:1_000 (add_stat ("dist",fun x -> x) (oneof [small_int_corners ();int])) (fun _ -> true);;
val t : Test.t = QCheck.Test.Test <abstr>
utop # QCheck_runner.run_tests ~verbose:true [t];;
random seed: 153870556
generated error fail pass / total     time test name
[✓] 1000    0    0 1000 / 1000     0.0s anon_test_1

+++ Stats for anon_test_1 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++

stats dist:
  num: 1000, avg: -55083208105414400.00, stddev: 1847115855773139200.00, median 9, min -4590718933436425025, max 4611686018427387903
  -4590718933436425025..-4130598685843234370: ##                                                               26
  -4130598685843234369..-3670478438250043714: #                                                                13
  -3670478438250043713..-3210358190656853058: ###                                                              37
  -3210358190656853057..-2750237943063662402: ###                                                              30
  -2750237943063662401..-2290117695470471746: ##                                                               27
  -2290117695470471745..-1829997447877281090: ##                                                               24
  -1829997447877281089..-1369877200284090434: ##                                                               27
  -1369877200284090433.. -909756952690899778: ##                                                               27
   -909756952690899777.. -449636705097709122: ##                                                               21
   -449636705097709121..   10483542495481534: #######################################################         531
     10483542495481535..  470603790088672190: ##                                                               21
    470603790088672191..  930724037681862846: ##                                                               27
    930724037681862847.. 1390844285275053502: ##                                                               24
   1390844285275053503.. 1850964532868244158: ##                                                               25
   1850964532868244159.. 2311084780461434814: ##                                                               28
   2311084780461434815.. 2771205028054625470: ##                                                               23
   2771205028054625471.. 3231325275647816126: ##                                                               23
   3231325275647816127.. 3691445523241006782: ##                                                               25
   3691445523241006783.. 4151565770834197438: #                                                                17
   4151565770834197439.. 4611686018427387903: ##                                                               24
  -4611686018427387713..-4151565770834197058:                                                                   0
================================================================================
success (ran 1 tests)
- : int = 0

After the change it behaves better:

utop # open QCheck;;
utop # QCheck_runner.set_seed 153870556;;
random seed: 153870556
- : unit = ()
utop # let t = Test.make ~count:1_000 (add_stat ("dist",fun x -> x) (oneof [small_int_corners ();int])) (fun _ -> true);;
val t : Test.t = QCheck2.Test.Test <abstr>
utop # QCheck_runner.run_tests ~verbose:true [t];;
generated error fail pass / total     time test name
[✓] 1000    0    0 1000 / 1000     0.0s anon_test_1

+++ Stats for anon_test_1 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++

stats dist:
  num: 1000, avg: -55083208105414400.00, stddev: 1847115855773139200.00, median 9, min -4590718933436425025, max 4611686018427387903
  -4590718933436425025..-4130598685843234370: ##                                                               26
  -4130598685843234369..-3670478438250043714: #                                                                13
  -3670478438250043713..-3210358190656853058: ###                                                              37
  -3210358190656853057..-2750237943063662402: ###                                                              30
  -2750237943063662401..-2290117695470471746: ##                                                               27
  -2290117695470471745..-1829997447877281090: ##                                                               24
  -1829997447877281089..-1369877200284090434: ##                                                               27
  -1369877200284090433.. -909756952690899778: ##                                                               27
   -909756952690899777.. -449636705097709122: ##                                                               21
   -449636705097709121..   10483542495481534: #######################################################         531
     10483542495481535..  470603790088672190: ##                                                               21
    470603790088672191..  930724037681862846: ##                                                               27
    930724037681862847.. 1390844285275053502: ##                                                               24
   1390844285275053503.. 1850964532868244158: ##                                                               25
   1850964532868244159.. 2311084780461434814: ##                                                               28
   2311084780461434815.. 2771205028054625470: ##                                                               23
   2771205028054625471.. 3231325275647816126: ##                                                               23
   3231325275647816127.. 3691445523241006782: ##                                                               25
   3691445523241006783.. 4151565770834197438: #                                                                17
   4151565770834197439.. 4611686018427387903: ##                                                               24
================================================================================
success (ran 1 tests)
- : int = 0

I'm still not too happy about the statistics code, but this is at least a step in the right direction.

[c-cube]

Good catch, thank you. I don't like the stats code either, but it has never been clean and it's the best we have right now :)