Relax ext-bcmath requirement in composer.json and instead add checks when attempting to use BinaryCalculator

[pointybeard]

Currently, there is a requirement for ext-bcmath to be installed:

unit-converter/composer.json

Lines 12 to 16 in a873250

	"require": {
	"php": "^7.3 || ^8.0",
	"ext-bcmath": "*",
	"ext-intl": "*"
	},

However, it is possible to use SimpleCalculator instead of BinaryCalculator:

unit-converter/src/Unit/AbstractUnit.php

Lines 128 to 135 in a873250

	* @return int|float|string
	*/
	public function as(UnitInterface $unit, int $precision = null, bool $binary = false)
	{
	return \UnitConverter\UnitConverter::createBuilder()
	->{'add'.(($binary) ? 'Binary' : 'Simple').'Calculator'}() # ¯\_(ツ)_/¯
	->addRegistryWith(array_unique([$this, $unit]))
	->build()

To give flexibility, and support systems that do not or cannot install php-bcmath, I suggest adding some assertions in AbstractUnit::as() or in BinaryCalculator to check that the bcmath extension is installed if someone is attempting to use the BinaryCalculator.

It appears this is approach is already taken for ext-intl here.

[pointybeard]

Looks like BinaryCalculator already has an assertion:

unit-converter/src/Calculator/BinaryCalculator.php

Lines 40 to 53 in a873250

	public function __construct(int $precision = null, int $roundingMode = null)
	{
	if (extension_loaded('bcmath')) {
	parent::__construct($precision, $roundingMode);
	return;
	}
	$fqcn = explode('\\', static::class);
	throw new RuntimeException(sprintf(
	'Unable to construct a %s due to missing bcmath library. Please check your PHP extensions.',
	end($fqcn),
	));

So, it seems it just a matter of changing composer.json. ext-intl and ext-bcmath could be put into the suggest block of composer.json. E.g.

"suggest": {
    "ext-bcmath": "Needed to enable usage of BinaryCalculator",
    "ext-intl": "Needed to support spellout() feature of UnitConverter"
}