def p_relexpr(p):
 p[0] = ('RELOP', p[2], p[1], p[3])

def p_relexpr ( p ) : p [ 0 ] = ( 'RELOP' , p [ 2 ] , p [ 1 ] , p [ 3 ] )
relexpr : expr lt expr | expr le expr | expr gt expr | expr ge expr | expr equals expr | expr ne expr .