Floating-point arithmetic isn't precise. You want to compare two floating-point numbers and know if they're equal when carried out to a certain number of decimal places. Most of the time, this is the way you *should* compare floating-point numbers for equality.

Use `sprintf`

to format the numbers to a certain number of decimal places, then compare the resulting strings:

# equal(NUM1, NUM2, ACCURACY) : returns true if NUM1 and NUM2 are # equal to ACCURACY number of decimal places sub equal { my ($A, $B, $dp) = @_; return sprintf("%.${dp}g", $A) eq sprintf("%.${dp}g", $B); }

Alternatively, store the numbers as integers by assuming the decimal place.

You need the `equal`

routine because most computers' floating-point representations aren't accurate. See the Introduction for a discussion of this issue.

If you have a fixed number of decimal places, as with currency, you can sidestep the problem by storing your values as integers. Storing `$3.50`

as `350`

instead of `3.5`

removes the need for floating-point values. Reintroduce the decimal point on output:

```
$wage = 536; # $5.36/hour
$week = 40 * $wage; # $214.40
printf("One week's wage is: \$%.2f\n", $week/100);
```*One week's wage is: $214.40*

It rarely makes sense to compare to more than 15 decimal places.

The `sprintf`

function in *perlfunc *(1) and Chapter 3 of Programming Perl; the entry on `$#`

in the *perlvar *(1) manpage and Chapter 2 of Programming Perl; the documentation for the standard Math::BigFloat module (also in Chapter 7 of Programming Perl); we use `sprintf`

in Recipe 2.3; Volume 2, Section 4.2.2 of The Art of Computer Programming