Turning Floats into Their Closest (UTF-8 Character) Fraction.

Question

I want to take any real number, and return the closest number, with the closest fraction as available in the UTF-8 character set, appropriate.

0/4 = 0.00 =   # < .125
1/4 = 0.25 = ¼ # > .125 & < .375
2/4 = 0.50 = ½ # > .375 & < .625
3/4 = 0.75 = ¾ # > .625 & < .875
4/4 = 1.00 =   # > .875

I made this function to do that task:

function displayFraction($realNumber)
{
    if (!is_float($realNumber))
    {
        return $realNumber;
    }
    list($number, $decimal) = explode('.', $realNumber);
    $decimal = '.' . $decimal;
    switch($decimal)
    {
        case $decimal < 0.125:
            return $number;
        case $decimal > 0.125 && $decimal < 0.375:
            return $number . '¼'; # 188 ¼ &#188;
        case $decimal > 0.375 && $decimal < 0.625:
            return $number . '½'; # 189 ½ &#189;
        case $decimal > 0.625 && $decimal < 0.875:
            return $number . '¾'; # 190 ¾ &#190;
        case $decimal < 0.875:
            return ++$number;
    }
}

What are the better / diffrent way to do this?

echo displayFraction(3.1) . PHP_EOL;      # Outputs: 3
echo displayFraction(3.141593) . PHP_EOL; # Outputs: 3¼
echo displayFraction(3.267432) . PHP_EOL; # Outputs: 3¼
echo displayFraction(3.38) . PHP_EOL;     # Outputs: 3½

Expand my mind!

Answer 1

You implemented a statically compiled search algorithm for picking the fractions. So long as the number of unicode fractions doesn't change much (which it won't), then what you have is fine. Move on.

If you lived in a world where the unicode fractions did change often. Then you should switch your search from being hard coded to data-driven. Just have a table of fraction values and their unicode equivalent. Search the table for the closest fraction, then use the associated unicode char.

Answer 2

One could be "clever" and take (188 + (decimal-0.125) * 4) for the case when decimal is between 0.125 and 0.875, but that would be more obfuscating than clever, IMO. That said, you probably want your last case to be > 0.875 and not < 0.875.

Answer 3

You shouldn't rely on the presence of a decimal part:

# Will generate a STRICT warning if $realNumber does not contain a full stop:
list($number, $decimal) = explode('.', $realNumber);

Try this instead:

$integerPart = floor($realNumber);
$decimalPart = $realPart - $integerPart;

You shouldn't use a switch here, but rather if statements (it will look like it's working but give unexpected results if you input 0, for example, since you are actually comparing $decimal to the result of the expression $decimal < 0.125):

if ($decimalPart <= 0.25) {
    # ...
} else if ($decimalPart <= 0.5) {
    # ...
} else if ...