function accumulator( input ) {
		if ( arguments.length === 0 ) {
			return acc();
		}
		return acc( sloc( input ) );
	}
If provided a value, the accumulator function returns an updated source lines of code (SLOC) summary. If not provided a value, the accumulator function returns the current SLOC summary.

@private
@param {(string|Buffer)} [input] - input program
@throws {TypeError} must provide either a string or Buffer
@returns {Object} SLOC summary

@example
var sloc = accumulator();
// returns {}

sloc = accumulator( '"use strict";\n\nvar y = 5;\n' );
// returns {...}

sloc = accumulator( '"use strict";\n\nmodule.exports = "beep";\n' );
// returns {...}

sloc = accumulator();
// returns {...}