Using An Array To Power Weighted Distributions In Lucee CFML 5.3.8.201

test.cfm

<cfscript>

	// Our build-function is going to return a generator function that produces values
	// with the given weighted frequencies.
	next = buildWeightedDistribution([
		{ value: "a", percent: 10 },
		{ value: "b", percent: 20 },
		{ value: "c", percent: 70 }
	]);

	// By outputting 100 values, we should see occurrences that roughly match the defined
	// percentages from above.
	loop times = 100 {

		echo( next() & " " );

	}

	// ------------------------------------------------------------------------------- //
	// ------------------------------------------------------------------------------- //

	/**
	* I return a function that will produce values with the given distribution. Each entry
	* is expected to have two properties:
	* 
	* - value: the value returned by the generator.
	* - percent: the weight (0-100) of the value in the distribution.
	*/
	public function function buildWeightedDistribution( required array distributions ) {

		var index = [];
		var indexSize = 0;

		// In order to make it super easy to generate the next value in our series, we're
		// going to pre-compute an array in which each value is repeated as many times as
		// is required by its weight. So, a value that is supposed to be returned 30% of
		// the time will be repeated 30 times in our internal index.
		for ( var distribution in distributions ) {

			loop times = distribution.percent {

				index[ ++indexSize ] = distribution.value;

			}

		}

		// Now that we have our internal index of repeated values, our generator function
		// simply has to pick a random value from the index.
		return(
			() => {

				return( index[ randRange( 1, indexSize, "SHA1PRNG" ) ] );

			}
		);

	}

</cfscript>