remove flawed tests from t/op/rand.t

There is a section of code supposedly intended to check that
d_randbits bits is sane. AFIKT, the code was flawed from the start,
and has just become more broken since.

Initially it ran rand(1) many times and recorded the min and max.
It then (in a convoluted way involving logarithms) checked that
$max wasn't greater than 1.

I suspect that this code was (at least at one point during its initial
writing) supposed to check that the number of bit of precision in rand()
matched d_randbits. If that was the case, then it certainly wasn't doing
that.

Subsequently, extra bogus tests were added, e.g. that
    $max < (2 ** $randbits)
which it always will be, since it should be < 1.

Then the main test was inadvertently broken by a precedence issue
involving '!': I don't think this does what you think it does:

    unless (ok( !$max <= 0 or $max >= (2 ** $randbits)))

Then an extra check was added after each call to rand(1) in the loop that
the result was in the range 0..1. This check made all the other checks
that follow on $min and and $max superfluous.

So this commit removes all those extra tests, and changes a couple
of 'print #...\n"' into diag("..."), since we're now in the 21st century
:-)

diff --git a/t/op/rand.t b/t/op/rand.t
index b3bfdd4..15a633d 100644 (file)
--- a/t/op/rand.t
+++ b/t/op/rand.t
@@ -24,7 +24,7 @@ use strict;
 use Config;
 
 require "./test.pl";
-plan(tests => 10);
+plan(tests => 7);
 
 
 my $reps = 15000;      # How many times to try rand each time.
@@ -47,17 +47,18 @@ sub bits ($) {
     my($off, $shouldbe);       # Problems with randbits
     my($dev, $bits);           # Number of one bits
     my $randbits = $Config{randbits};
-    $max = $min = rand(1);
+    $max = -1;
+    $min = 2;
     for (1..$reps) {
        my $n = rand(1);
        if ($n < 0.0 or $n >= 1.0) {
-           print <<EOM;
-# WHOA THERE!  \$Config{drand01} is set to '$Config{drand01}',
-# but that apparently produces values < 0.0 or >= 1.0.
-# Make sure \$Config{drand01} is a valid expression in the
-# C-language, and produces values in the range [0.0,1.0).
-#
-# I give up.
+           diag(<<EOM);
+WHOA THERE!  \$Config{drand01} is set to '$Config{drand01}',
+but that apparently produces values ($n) < 0.0 or >= 1.0.
+Make sure \$Config{drand01} is a valid expression in the
+C-language, and produces values in the range [0.0,1.0).
+
+I give up.
 EOM
            exit;
        }
@@ -71,55 +72,6 @@ EOM
        $min = $n if $n < $min;
     }
 
-
-    # This test checks for one of Perl's most frequent
-    # mis-configurations. Your system's documentation
-    # for rand(2) should tell you what value you need
-    # for randbits. Usually the diagnostic message
-    # has the right value as well. Just fix it and
-    # recompile, and you'll usually be fine. (The main 
-    # reason that the diagnostic message might get the
-    # wrong value is that Config.pm is incorrect.)
-    #
-    unless (ok( !$max <= 0 or $max >= (2 ** $randbits))) {# Just in case...
-       print <<DIAG;
-# max=[$max] min=[$min]
-# This perl was compiled with randbits=$randbits
-# which is _way_ off. Or maybe your system rand is broken,
-# or your C compiler can't multiply, or maybe Martians
-# have taken over your computer. For starters, see about
-# trying a better value for randbits, probably smaller.
-DIAG
-
-       # If that isn't the problem, we'll have
-       # to put d_martians into Config.pm 
-       print "# Skipping remaining tests until randbits is fixed.\n";
-       exit;
-    }
-
-    $off = log($max) / log(2);                 # log2
-    $off = int($off) + ($off > 0);             # Next more positive int
-    unless (is( $off, 0 )) {
-       $shouldbe = $Config{randbits} + $off;
-       print "# max=[$max] min=[$min]\n";
-       print "# This perl was compiled with randbits=$randbits on $^O.\n";
-       print "# Consider using randbits=$shouldbe instead.\n";
-       # And skip the remaining tests; they would be pointless now.
-       print "# Skipping remaining tests until randbits is fixed.\n";
-       exit;
-    }
-
-
-    # This should always be true: 0 <= rand(1) < 1
-    # If this test is failing, something is seriously wrong,
-    # either in perl or your system's rand function.
-    #
-    unless (ok( !($min < 0 or $max >= 1) )) {  # Slightly redundant...
-       print "# min too low\n" if $min < 0;
-       print "# max too high\n" if $max >= 1;
-    }
-
-
     # This is just a crude test. The average number produced
     # by rand should be about one-half. But once in a while
     # it will be relatively far away. Note: This test will
@@ -127,9 +79,8 @@ DIAG
     # See the hints for test 4 to see why.
     #
     $sum /= $reps;
-    unless (ok( !($sum < 0.4 or $sum > 0.6) )) {
-       print "# Average random number is far from 0.5\n";
-    }
+    ok($sum >= 0.4 && $sum <= 0.6)
+       or diag("Average random number ($sum) is far from 0.5");
 
 
     #   NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE