I've done some testing with large numbers and floats in Perl and JavaScript. Here are the results:
use strict;
use warnings;
my $NUM_A = 3335.999999999995;
my $NUM_B = 3335.99999999995;
# Normally, a 64-bit float can have 15 significant digits,
# which is the mantissa of a number. If you try to write
# 16 significant digits, you will lose precision!! And
# that's what happens with $NUM_A. It has 16 significant
# digit, and that's too long!
# In JavaScript, you can store 3335.9999999999995 which
# has 17 significant digits, but the numbers turns into 3336
# once you squeeze in another '9' in that list!
#
# In JavaScript, the largest mantissa you can have is:
# 9007199254740992. If you try to add 1 to this number,
# then the addition won't register, because it gets rounded
# back to the original number. lol
#
# In JavaScript, if you try to add
# 3335.9999999999995 + 0.0000000000001, it is equal to:
# 3335.9999999999995
# So the addition won't even register, because it considers
# that addition insignificantly small. The result won't change.
#
# In perl, it turns into 3336. lol
#
print " ADDITION: ", 3335.9999999999995 + 0.0000000000001, "\n";
print " SUBTRACT: ", 3335.9999999999995 - 0.0000000000001, "\n";
# Let's see what perl will do with this large number:
print " BIGGEST JAVASCRIPT NUMBER: ", 9007199254740992, "\n";
print " BIGGEST JAVASCRIPT NUMBER: ", 900719925474099, "\n";
print " BIGGEST JAVASCRIPT NUMBER: ", 90071992547409, "\n";
print " BIGGEST JAVASCRIPT NUMBER: ", 9007199254740, "\n";
print " BIGGEST JAVASCRIPT NUMBER: ", 900719925474, "\n";
# "print" won't display the last significan digit.
# so let's try this instead:
if (9007199254740988 > 9007199254740987) { print "1 BIGGER OK.\n" } #
+ prints fine
if (9007199254740989 > 9007199254740988) { print "2 BIGGER OK.\n" } #
+ prints fine
if (9007199254740990 > 9007199254740989) { print "3 BIGGER OK.\n" } #
+ prints fine
if (9007199254740991 > 9007199254740990) { print "4 BIGGER OK.\n" } #
+ prints fine
if (9007199254740992 > 9007199254740991) { print "5 BIGGER OK.\n" } #
+ prints fine
if (9007199254740993 > 9007199254740992) { print "6 BIGGER OK.\n" } #
+ <<this won't print!
if (9007199254740994 > 9007199254740993) { print "7 BIGGER OK.\n" } #
+ prints fine
if (9007199254740995 > 9007199254740994) { print "8 BIGGER OK.\n" } #
+ prints fine
if (9007199254740996 > 9007199254740995) { print "9 BIGGER OK.\n" } #
+ <<this won't print!
# See, as we start heading above that number,
# we have problems in perl as well.
# You can't tell whether a number is bigger or smaller,
# because the last digit get rounded when it is stored in memory.
# Okay, let's talk about divisions and remainders for a sec...
print " NUM_A = $NUM_A \n NUM_B = $NUM_B\n";
my $R = $NUM_B % 3330;
print " NUM_B % 3330 = $R (This should be 5.99999999995, but due to t
+he strange way 64-bit floats are stored, it gets \"corrupted.\" So, n
+ormally you'd get 5.9999999999499778. But in perl you don't even get
+that result. You just get 5.)\n\n";
# So, in order to get the same result you would get
# in JavaScript, you would call FMOD() function (see below)
# instead of using the % (mod) operator:
print " FMOD(NUM_B, 3330) = ", FMOD($NUM_B, 3330), "\n\n";
#
# This function produces the same result as the % operator
# in JavaScript: C = A % B;
#
# Usage: C = FMOD(A, B)
#
sub FMOD
{
my ($A, $B) = @_;
return $A - int($A / $B) * $B;
}
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