 values that
contain the right and left locations of what the terminal or
non-terminal covers in the input file.  These values must be properly
initialized in the terminals by the lexer. The left and right values
then propagate to non-terminals to which productions reduce.</p><p>
If there are several productions for the same non-terminal they may be 
declared together.  In this case the productions start with the non-terminal 
and "<tt>::=</tt>".  This is followed by multiple right hand sides each 
separate