program:	{ newline | section | statement }

newline:	[ space ] NEWLINE

space:		SPACE { SPACE }

section:	"." WORD newline

statement:	( function | space [ instruction ] ) [ space ] newline

function:	name [ space ] ":"

name:		WORD

instruction:	operator [ space [ operand_list ] ]

operator:	WORD

operand_list:	operand [ space ] { "," [ space ] operand [ space ] }

operand:	value | "[" value "]"

value:		symbol | register | immediate

symbol:		WORD

register:	"%" WORD

immediate:	"$" NUMBER