Upgrading A Built-In Function To A First-Class Citizen In Lucee 5.3.2.77

snippet-1.cfm

<cfscript>

	values = values.map( trim );

</cfscript>

snippet-2.cfm

<cfscript>

	operator = ( doUppercase )
		? ucase
		: lcase
	;

	echo( operator( "I said Good-Day, sir." ) );

</cfscript>

test.cfm

<cfscript>

	values = [ "oLLeH", "Ym", "dOOg", "DnEiRf" ];

	// NOTE: The .map() operations in the following calls will pass-in several arguments
	// to the provided operator ("reverse", "ucase", "lcase"); however, these Functions
	// can only accept one argument. As such, our proxy function will pare down the
	// arguments based on built-in function's native arity.

	values = values.map( upgradeBIF( "reverse" ) );

	// Randomly choose an operator for our next .map() call.
	operator = randRange( 0, 1 )
		? upgradeBIF( "ucase" )
		: upgradeBIF( "lcase" )
	;

	dump( values.map( operator ) );

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

	/**
	* I attempt to upgrade the given built-in function (BIF) such that it can be passed-
	* around like a first-class Function reference.
	* 
	* @name I am the name of the BIF to upgrade.
	*/
	public Function function upgradeBIF( required string name )
			cachedWithin = "request"
		{

		var bifMetadata = getFunctionData( name );
		// The getFunctionData() function returns meta-data about the built-in function
		// with the given name. This includes the array of arguments that it expects,
		// which can use to determine the arity of the function (ie, how many arguments
		// it expects).
		var bifArity = bifMetadata.arguments.len();

		return(
			() => {

				// If there are no arguments - the Built-In Function (BIF) doesn't expect
				// arguments - pass-through an empty set of arguments.
				if ( ! bifArity || ! arguments.len() ) {

					var argumentList = "";

				// If the arguments passed to the proxy function are provided as an
				// ordered list of values, then we have to pare down the collection to
				// just those expected by the Built-In Function's (BIF) native arity (or
				// ColdFuison will throw an error).
				// --
				// NOTE: We are loosely determining argument-type by seeing if an index-
				// oriented argument key exists.
				} else if ( arguments.keyExists( "1" ) ) {

					var argumentList = arguments
						.keyArray()
						.slice( 1, min( bifArity, arguments.len() ) )
						.map( ( index ) => "arguments[ #index# ]" )
						.toList( "," )
					;

				// If the arguments passed to the proxy function are provided as a set of
				// key-value pairs, then we need to pass them through to the Built-In
				// Function (BIF) in the same manner.
				// --
				// CAUTION: While some BIFs support argumentCollection (those that are
				// implemented in CFML), the vast majority of BIFs do not support this
				// type of invocation. As such, we have to explicitly create a listed of
				// named arguments.
				} else {

					var argumentList = arguments
						.keyArray()
						.map( ( key ) => "#key# = arguments.#key#" )
						.toList( "," )
					;

				}

				return( evaluate( "#name#( #argumentList# )" ) );

			}
		);

	}

</cfscript>