一种新语言的语法

Question

我有这种语法，我无法理解如何为其创建解析器：

    module = properties fields methods module#3 'end'

properties = list#0 (property add#2)*
property = 'class' 'name' class# ';'

fields = list#0 (field add#2)*
field = type list#0 id add#2 [';'/','] ! (',' id add#2)* ';' field#2

methods = list#0 (method add#2)*
method = (type id / nothing#0 id) ! '(' args ')' follow method#4
args = list#0 (arg add#2 (',' arg add#2)*)?
arg = type id ! arg#2 / nothing#0 id ! arg#2

statements = list#0 (statement add#2)*
statement = do / jump / compound / simple
follow = block / jump / compound / simple
jump = break / continue / return
compound = if / while
simple = local / assign

do = 'do' '{' statements '}' do#1
block = '{' statements '}' block#1

break = 'break' ';' break#0
continue = 'continue' ';' continue#0
return = 'return' (exp / nothing#0) ';' return#1

if = 'if' '(' exp ')' follow ('else' follow / nothing#0) if#3
while = 'while' '(' exp ')' follow while#2

local = type id ! init? local#2 ';'
init = 'assign' exp assign#2 / '.' id dot#2 '(' exps ')' call#2
assign = id 'assign' ! exp assign#2 ';'

exp = id ( '(' exps ')' call#2 / '.' id dot#2 '(' exps ')' call#2 )?
exps = list#0 (exp add#2 (',' exp add#2)*)?
type = 'name' type#
id = 'name' id#

'.' = 'DOT'

谁能让我理解这个语法。 谢谢

Answer 1

这个：

module = properties fields methods module#3 'end'

意思是：

a module consists of properties, followed by fields, followed by methods, followed by the word "end"

因此，为了解析模块，编译器应：

parse properties
parse fields
parse methods
match the word "end"

带“＃”的项目是应创建的语法节点的类型，该数字指示应将多少先前的解析结果传递给它。

在Python语言中，代码可能看起来像这样：

def parse_module():
    properties = parse_properties()
    fields = parse_fields()
    methods = parse_methods()
    module = make_module(properties, fields, methods)
    match("end")
    return module

“ /”分隔替代项，“（...）*”表示任意数量的重复项，“？” 表示可选项目。