spec.md

规范

每个步骤结尾的 规范 一节都会对这个步骤中的新特性给出规范，方便大家查阅。

step12 语法规范

灰色部分表示相对上一节的修改。

program
    : (function | declaration)*

function
    : type Identifier '(' parameter_list ')' ( compound_statement | ; )

type
    : 'int'

parameter_list
    : (type Identifier ('[' ']')?(('['Integer']')*)? (',' type Identifier ('[' ']')?(('['Integer']')*)?)*)?

compound_statement
    : '{' block_item* '}'

block_item
    : statement
    | declaration

statement
    : 'return' expression ';'
    | expression? ';'
    | 'if' '(' expression ')' statement ('else' statement)?
    | compound_statement
    | 'for' '(' expression? ';' expression? ';' expression? ')' statement
    | 'for' '(' declaration expression? ';' expression? ')' statement
    | 'while' '(' expression ')' statement
    | 'break' ';'
    | 'continue' ';'

declaration
    : type Identifier ('=' expression)? ';'
    | type Identifier ('[' Integer ']')+ ('=' '{' (Integer (',' Integer)*)? '}')? ';'


expression_list
    : (expression (',' expression)*)?

expression
    : assignment

assignment
    : conditional
    | unary '=' expression

conditional
    : logical_or
    | logical_or '?' expression ':' conditional

logical_or
    : logical_and
    | logical_or '||' logical_and

logical_and
    : equality
    | logical_and '&&' equality

equality
    : relational
    | equality ('=='|'!=') relational

relational
    : additive
    | relational ('<'|'>'|'<='|'>=') additive

additive
    : multiplicative
    | additive ('+'|'-') multiplicative

multiplicative
    : unary
    | multiplicative ('*'|'/'|'%') unary

unary
    : postfix
    | ('-'|'~'|'!') unary

postfix
    : primary
    | Identifier '(' expression_list ')'

    | postfix '[' expression ']'

primary
    : Integer
    | '(' expression ')'
    | Identifier

step12 语义规范

12.1 多维数组按照类似一维数组的初始化方法，不要求实现内部嵌套括号

int a[2][2] = {1, 2, 3, 4};

会将数组变为

a[0][0] = 1;

a[0][1] = 2;

a[1][0] = 3;

a[1][1] = 4;

12.2 数组传参是支持不定长度的

int fun(int a[]) 是被支持的，由于传参不需要申请完整的数组的空间，不会产生需要计算数组空间的问题