IEEE floating point numbers are wrongly over-trusted in calculations. Observe:

print "---\n"; print "A: ", 2.4, "\n"; print "B: ", 0.2*12, "\n"; if ( 0.2*12 == 2.4 ) { print "These are equal.\n"; } else { print "These are not equal.\n"; } A: 2.4 B: 2.4 These are not equal.

This is the result of the fact that 0.2 ( 1/5 ) cannot be represented as a binary fraction in IEEE space.

Thus, if you're checking floating-point equality, use `sprintf`

or similar.

See http://perldoc.perl.org/perlfaq4.html for details.

Submit a PR to github.com/petdance/perl101

© 2007-2018 Andy Lester