BNF

// program :global_compound_statement
// global_compound_statement:statement_local|func_def|class_def
// class_def: KEY_CLASS variable {INHERIT variable} assignment_statement|class_func_def LBRCS  RBRCS
// class_func_def: func variable LPAREN empty|expr(,expr)* RPAREN LBRCS statement_local RBRCS
// func_def: func variable LPAREN empty|expr(,expr)* RPAREN LBRCS statement_local RBRCS
// assignment_statement  :variable(,variable)* (ASSIGN|PLUS_EQ|MINUS_EQ|MULTI_EQ|DIV_EQ|MOD_EQ) expr(,expr)*
// statement_local: expr|empty|break_statement|continue_statement|return_statement|if_statement|foreach_statement|assignment_statement|for_statement
// foreach_statement: KEY_FOREACH variable COMMA variable ASSIGN expr LBRCS statement_local RBRCS
// break_statement: KEY_BREAK
// continue_statement: KEY_CONTINUE
// if_statement: KEY_IF {assignment_statement SEMICOLON} expr LBRCS statement_local RBRCS (KEY_ELIF {assignment_statement SEMICOLON} expr LBRCS statement_local RBRCS)* {KEY_ELSE {assignment_statement SEMICOLON} expr LBRCS statement_local RBRCS}
// return_statement: KEY_RETURN expr(,expr)|empty
// for_statement: KEY_FOR (expr)|(assignment_statement|empty SEMICOLON expr|empty SEMICOLON expr|empty) LBRCS statement_local RBRCS

// expr       :tuple(COMMA tuple)*
// tuple      :or(OR or)*
// or         :and(AND and)*
// and        :compare((GREAT|LESS|GEQ|LEQ|EQUAL|NOT_EQ)compare)*
// compare    :{NOT}not
// not        :{VIRGULE}bitor
// bitor      :xor (XOR xor)*
// xor        :bitand(REF bitand)*
// bitand     :shift (LSHIFT|RSHIFT shift)*
// shift      :term((PLUS|MINUS)term)*
// term       :negpos((MUL|DIV|MOD)negpos)*
// negpos     :{PLUS|MINUS}factor
// factor     :(REVERSE)reverse
// reverse    :selfaddsub(PLUS_PLUS|MINUS_MINUS)
// selfaddsub :attribute(QUOTE attribute)*
// attribute  :index (LBRK expr RBRK)*
// attribute  :index(LBRK expr:expr RBRK)*
// index      :func_call(LPRNTH empty|tuple(,tuple)* RPRNTH)*
// func_call  :{LBRK} list (COMMA list)* {LBRK}
// list       :{LBRCS} tuple:tuple (COMMA tuple:tuple )* {LBRCS}|dict
// dict       :variable|INTEGER|STRING|DOUBLE|BOOLEAN|NULL|LPRNTH expr RPRNTH
// variable   :ID
// empty      :

                        表达式                expr
,                       元组                  tuple
||                      布尔“或”               or
&&                      布尔“与”               and
<，<=，>，>=，!=，==     比较                   compare
!                       布尔“非”               not
|                       按位或                 bitor
^                       按位异或               xor
&                       按位与                 bitand
<<，>>                  移位                   shift
+，-                    加法与减法              term
*，/，%                 乘法、除法与取余         front_op
-------------------------前置运算符-------------------------
+x，-x                  正负号                 back_op
~x                      按位翻转               back_op
=========================前置运算符=========================
x--,x++                 自增，自减             base_tp
x.attribute             属性参考               base_tp
x[index]                下标                   base_tp
x[index:index]          寻址段                 base_tp
f(arguments...)         函数调用               base_tp

[expression,...]        列表显示               list
{key:datum,...}         字典显示               dict
(variable)              绑定                   bind