====== FNEXT() ======
Returns an availble file channel. -1 when none are available. 

**Example:**  

		println "The next available file channel is ",FNEXT()

`FNEXT` was created in order to better support code libraries made possible by functions and procedures. File channel numbers can now be determined at runtime.  

**CAUTION:** Until you actually OPEN a file FNEXT will return the same value over and over.  

		chan1 = FNEXT() chan2 = FNEXT()  WRONG! chan1 will equal chan2 )  
		
another gotcha: FOPEN FNEXT(),blah blah  
There is no way to determine what channel was used to open the file!  

Here's an example of how it should be used:  

		chan1 = FNEXT() FOPEN   chan1,...  
		chan2 = FNEXT() FOPEN   chan2,...  

**See also:** FOpen FClose FCreate FAppend FRewind FCloseAll