program = _{SOI~statement* ~ EOI}

statement  = _{
     emptyStatement
    |importStatement ~eos?
    |assignStatement~eos?
    |setStatement~eos?
    | controlFlow ~ eos?

    | definitions~ eos?
     | expr~eos?
    |data
}
controlFlow = _{ifStatement|forStatement}
definitions = _{function_define|type_statement}
/*====================================================================================================================*/
emptyStatement = {eos | Separate}
eos            = {Semicolon}
comma_or_semi = _{Comma|Semicolon}
/*====================================================================================================================*/
//FIXME: 修复 nested using
importStatement = _{
    Use ~use_alias|Use ~use_module_select|Use ~use_module_string
}
use_module_select = !{ moduleName ~  (( Dot | Proportion|With) ~ moduleSelect)? }
use_module_except = !{ moduleName ~ (Slash|Except) ~ moduleSelect }

use_module_string = !{ String ~ (With ~moduleSelect)?}

moduleName = {namespace| maybeSymbol|SYMBOL} // MaybeSymbol as Namespace here
moduleSelect = { Star | "{"~idTuples~ ( comma_or_semi? ~ idTuples)* ~comma_or_semi?~"}"}
idTuples={use_alias|use_module_select}
use_alias = !{ moduleName~As~SYMBOL}
///#C678DD
Cover = ${Star}
//!#C678DD: Use|Expose|With|Except|As
Use  =@{"use"}
Expose   =@{"expose"}
With = @{"with"}
Except = @{"except"}
As    =@{"as"}
/*====================================================================================================================*/


block = !{
"{" ~ statement* ~ "}"
| Begin ~ (!End~statement)*~ End
|Begin ~ expr
}
suite= !{
     "{" ~ statement* ~ "}"
     | Begin ~ statement*
}
//!#56B6C2: Begin|End
Begin = @{"begin"|Colon}
End =@{"end"|"\u{AD}"}
/*====================================================================================================================*/
expr = !{
    term ~ (!NEWLINE~ slice)
  | trinoculars
  | slot_function | lambda_function
  | term ~ (Infix ~ term)*
}
term =  { Prefix* ~ node ~ Postfix* }
node = _{  data| "(" ~ expr ~ ")" }
condition  = { node|expr}
expressions = {"("~expr~ ( comma_or_semi? ~ expr)* ~comma_or_semi?~")"}
trinoculars = _{if_trinocular}
expr_or_block = {expr|"{"~statement+~"}"}
/*====================================================================================================================*/
functionApply = {
    function_name ~ "(" ~ expr? ~")"|
    function_module? ~ function_name ~ "(" ~ expr? ~")"
}
methodApply = {expr ~Dot ~ function_name ~ "(" ~ expr? ~")"}


///#61AFEF
function_name = {SYMBOL}
function_module = {(namespace ~ Dot)? ~ (SYMBOL ~ Dot)*}
/*====================================================================================================================*/
//!#C678DD: Pass|Return|Break
Pass = @{"pass"}
Return = @{"return"}
Break = @{"break"}
/*====================================================================================================================*/
ifStatement =_{if_nested_else|if_nested|if_single_else|if_single}
if_single = { If~condition~ if_then_block}
if_nested = { If~ condition~ if_then_suite ~ else_if_suite+}//FIXME: 无效语法
if_single_else = { If~condition~ if_then_suite ~ Else ~ if_then_block}
if_nested_else = { If~ condition~ if_then_suite~ else_if_suite+ ~Else ~ if_then_block}
if_trinocular = {
    term ~ Question ~ term ~ Colon ~ term
  | term ~ If ~ term ~ Else ~ term
}
else_if_suite = !{ elif ~condition~ if_nest_suite}
else_if_block = !{ elif ~condition~ if_then_block}
if_nest_suite = _{
    "{" ~ statement+ ~ "}"
   | Begin? ~ (!if_forbidden~statement)
   | Begin? ~ (!if_forbidden~statement)+ ~ End?
}
if_then_suite = _{
    "{" ~ statement+ ~ "}"
   | Begin? ~ (!if_forbidden~statement)+ ~ End?
}
if_then_block = _{
    "{" ~ statement+ ~ "}"
  | Begin? ~ (!End~statement)+~ End
  | Begin? ~ (!End~expr)
}
elif = _{Ef|Else ~ If}
if_forbidden = _{If|Else|elif}
//!#C678DD: Ef|If|Else
Ef = @{"ef"}
If = @{"if"}
Else = @{"else"}
/*====================================================================================================================*/
switchStatement = {Switch}


//!#C678DD: If|Else
Switch =@{"switch"}
Case =@{"case"}


/*====================================================================================================================*/
forStatement = _{For ~forLoop|For ~forInLoop}
forLoop = {expressions ~block}


forInLoop = {SYMBOL~In~expr~block}

//!#C678DD: For|In
For = @{"for"}
In = @{"in"}
/*====================================================================================================================*/

/// #E06C75
type_expr = { type_term ~ (Infix ~ type_term)* | data | functionApply}
/// #E06C75
type_term =  { Prefix* ~ type_node ~ Postfix* }
type_node = _{  "(" ~ type_expr ~ ")"  }
/// #E06C75
type_atom = ${type_symbol|Integer}
/// #E06C75
type_symbol = ${Symbol}
type_prefix = _{type_expr~ Symbol}
type_suffix = _{"<:"~type_expr}

type_statement = {Type~type_symbol~type_block}
type_block = !{
"{" ~ type_expr ~ "}"
|Begin ~ type_expr ~ End?
}

//!#C678DD: Type|To
Type = @{"type"}
/*====================================================================================================================*/
assignStatement = {Var ~ (!assign_pair ~ modifier)* ~assign_pair}
assign_name = {SYMBOL~type_suffix?}
assign_pair = {assign_name ~ block}

setStatement = _{ SYMBOL ~Set ~expr }

///Orange
modifier = ${Symbol}
//!#C678DD: Val|Var
Var = @{"var"}
Val = @{"val"}


/*====================================================================================================================*/




function_define = {Def ~ (!function_body ~modifier)*~  function_body~ type_suffix? ~ block }
function_body = _{function_name ~ lambda_body    |function_name ~ "(" ~ ")"}


function_parameter = {type_expr~ function_symbol|function_symbol}
function_symbol = {Symbol~ Star?}
function_define_block = !{
	"{" ~ statement* ~ "}"
	| Begin ~ (!End~statement)*~ End
	|Begin ~ expr
}
///#C678DD
Def = @{"def"}
/*====================================================================================================================*/
slot_function = {term ~ Ampersand}
lambda_function = {lambda_body~To~expr_or_block}
lambda_body = _{"(" ~function_parameter ~ ( comma_or_semi? ~ function_parameter )* ~comma_or_semi?~ ")"}
//!#C678DD: Ampersand
///#A6E22E
SlotSymbol = @{Dollar~(SYMBOL|Integer)}
SlotMark = ${Dollar}
/*====================================================================================================================*/
traitStatement = { trait_head ~"{" ~ traitExpression*  ~ "}"   }
trait_head = _{Trait ~ SYMBOL ~classExtend? ~classTrait?}
traitExpression = {interfaceExpression | structureExpression}
classExtend =${"classExtend"}
classTrait = ${"classTrait"}

/*====================================================================================================================*/
interfaceStatement = {      interface_head~"{"~ interfaceExpression* ~"}"    }
interface_head = _{Interface ~SYMBOL~ classExtend? ~classTrait?}
interfaceExpression= { interfaceFunction ~Colon ~type_expr~comma_or_semi?}
interfaceFunction= { SYMBOL ~"(" ~interfaceParameters? ~")"~ nullable?}
interfaceParameters= { type_expr ~SYMBOL ~ (Comma ~type_expr~ SYMBOL )*}

nullable = ${"?"}

/*====================================================================================================================*/
structure_statement  = {  structure_head~"{" ~structureExpression* ~"}" }
structure_head = _{Structure ~SYMBOL ~classExtend? ~classTrait?}
structureExpression= { SYMBOL~ nullable~ Colon~ type_expr ~comma_or_semi?}

/*====================================================================================================================*/
enumerateStatement  = {      enumerate_head~"{" ~enumerateExpression* ~"}"   }
enumerate_head = _{Enumerate ~(Plus | Star)? ~SYMBOL ~classExtend? ~classTrait?}
enumerateExpression= { SYMBOL ~comma_or_semi? | SYMBOL ~ Colon~ enumerateNumber~ comma_or_semi?}
enumerateNumber= { Number | SYMBOL ~ Or ~SYMBOL}
/*====================================================================================================================*/
///#C678DD
name_head = ${(Local| Class)?~Proportion}
//!#C678DD: Trait|Interface|Structure|Enumerate
Trait      =@{"trait"}
Interface  =@{"interface"}
Structure  =@{"structure"}
Enumerate = @{"enumerate"}
Local =@{"local"}
Class =@{"class"}
/*====================================================================================================================*/
data =  {dict|list|Null|Boolean|Byte|Number| String |Symbol|SlotSymbol}
dict  = {  "{" ~key_value? ~(Comma ~key_value)* ~Comma? ~"}"}
list     ={ "[" ~element? ~(Comma ~element)* ~Comma? ~"]"}
slice  ={"[" ~index ~(Comma ~index)* ~Comma? ~"]"}
index = {    index_step|index_range|index_element}
key_value =!{key_valid ~ Colon ~element}
key_valid =!{Integer | SYMBOL | String}
element  =!{data | expr | statement}
index_element = !{element}
index_range = !{element? ~ Colon ~ element?}
index_step = !{element? ~ Colon ~ element?~ Colon ~ element?}
/*====================================================================================================================*/



/*====================================================================================================================*/
///#D19A66
Null = @{"null"}
/*====================================================================================================================*/
///#D19A66
Boolean = !{ True | False }
True = @{"true"}
False =@{"false"}
/*====================================================================================================================*/
///#D19A66
Byte = ${Byte_BIN|Byte_OCT| Byte_HEX}//TODO: 广义 0 前导
Byte_BIN = ${ Zero ~ B ~ (Underline? ~ ASCII_BIN_DIGIT)+ }
Byte_OCT = ${ Zero ~ O ~ (Underline? ~ ASCII_OCT_DIGIT)+ }
Byte_HEX = ${ Zero ~ X ~ (Underline? ~ ASCII_HEX_DIGIT)+ }
/*====================================================================================================================*/
//!#D19A66: Integer|Decimal|DecimalBad|Exponent|ComplexHandler
Number = ${Exponent|Complex|Decimal|DecimalBad|Integer}
Decimal       = ${Integer ~Dot~ ASCII_DIGIT+}
DecimalBad   = ${Integer~Dot | Dot~ASCII_DIGIT+}
Exponent = ${(Decimal|Integer) ~E~ (Decimal|Integer)}
Complex = ${(Decimal|Integer)~ ComplexHandler}
Integer = @{ Zero|ASCII_DIGIT ~ (Underline? ~ ASCII_NONZERO_DIGIT)* }
ComplexHandler = @{SYMBOL}
/*====================================================================================================================*/
///#98C379
String = ${StringSingle|StringBlock|LiteralString| LiteralBlock}//TODO: 字符串表达式
StringSingle = ${ S2 ~ (!S2~ ANY)* ~ S2 }
StringBlock = ${ S6 ~ (!S6~ ANY)* ~ S6 }
LiteralString= ${ S1 ~ (!S1~ ANY)* ~ S1 }
LiteralBlock = ${ S3 ~ (!S3~ ANY)* ~ S3 }
/*====================================================================================================================*/
Symbol = ${maybeSymbol|mustSymbol| SYMBOL}
mustSymbol = ${namespace~(Dot~SYMBOL)+}
maybeSymbol = ${SYMBOL~ (Dot~SYMBOL)+}
namespace = ${name_head? ~ SYMBOL ~ (Proportion ~ SYMBOL)+}



///#E5C07B
// SYMBOL = @{NameStartCharacter~ NameCharacter*}
NameCharacter = _{ASCII_DIGIT| NameStartCharacter}
NameStartCharacter = _{Underline | ASCII_ALPHA}
/*====================================================================================================================*/
// NEWLINE = @{"\r"~"\n"|"\r"|"\n"}
WHITESPACE = _{NEWLINE|SPACE_SEPARATOR | "\t"}
///#7F848E
COMMENT = ${Shebang|SingleLineComment| MultiLineComment}
Shebang = ${"#!" ~ (!NEWLINE ~ ANY)*}
SingleLineComment = _{   "///" ~ (!NEWLINE ~ ANY)*}
MultiLineComment = _{    "%%%" ~ (MultiLineComment | !"%%%" ~ ANY)* ~ "%%%"}

/*====================================================================================================================*/
Keywords = _{Val|Var|Def|Use} //TODO: 删除
Zero = _{"0"}
E = _{"e"|"E"}
X = _{"x"|"X"}
O = _{"o"|"O"}
B = _{"b"|"B"}




//!#56B6C2: Infix
Prefix = ${Plus|Minus|Increase|Decrease}
Postfix = ${"!"|Ampersand}
Infix = ${o_add|o_times}


Set = @{"="}

Or = @{"|"}
LazyOr = @{"||"}


Star     =@{"*"}
Slash    =@{"/"}

Proportion = @{"::"|"∷"}//U+2237
Comma  =@{","|"，"} //U+FF0C
Dot = @{"."}
Separate       = @{";;"}
Semicolon      = @{";" | "；"}  //U+FF1B
//!#56B6C2: Question|Colon
Colon = @{":"|"："} //U+FF1A
Question=@{"?"}
Underline = @{"_"}



Import    =@{"<<<"|"⋘"} //U+22D8
Export   =@{">>>"|"⋙"}    //U+22D9
LeftShift   =@{"<<"|"≪"}  //U+226A
RightShift =@{">>"|"≫"}   //U+226B
LessEqual   =@{"<="}
GraterEqual =@{">="}
Less        =@{"<"}
Grater      =@{">"}



Equivalent   =@{"==="}
NotEquivalent =@{"=!="}
Equal         =@{"=="}
NotEqual   =@{"!="|"≠"} //U+2260






o_add = _{Plus|Minus}
Plus =@{"+"}
Minus =@{"-"}
o_times = _{Multiply|CenterDot|Kronecker|TensorProduct|Divide|Quotient |Modulo  }
Multiply =@{Star | "×"}  //U+00D7
CenterDot = @{"⋅"}   //U+22C5
Kronecker     =@{"⊗"}  //U+2297
TensorProduct=@{"⊙"} //U+2299
Divide   = @{Slash | "÷"}  //U+00F7
Quotient      = @{"//"}
Modulo    = @{"%"}
Remainder =@{"⁒"} //U+2052 //⸓

o_power= _{ Power  }
Power = @{"^"}
Surd  = @{"√"} //U+221A


Increase      =@{"++"}
Decrease       =@{"--"}


To =@{"->"}


Elvis      =@{":?"}
Map         =@ {"/@"}


Quote    =@{"`"}
Acute     =@{"´"} // U+00B4
S1 = _{"'"}
S2 = _{"\""}
S3 = _{"'''"}
S6 = _{"\"\"\""}



LogicOr    =@{"||"|"∧"}   //U+2227
LogicAnd  =@{"&&"|"∨"}   //U+2228
LogicNot  =@{"¬"}   //U+00AC

Ellipsis  =@{"..."|"…"} // U+2026


Dollar = @{"$"}
Ampersand = @{"&"}

/*
LogicXor      : '\u2295'; //U+2295 ⊕
MapAll        : '//@';

Output        : '%%';
/* =~ */
Concat        : '~~';
Destruct      : '~=';
/* |&! */

DoubleBang : '!!';
BitNot     : '!' | '\uFF01'; //U+FF01 ！


/* $ @ */
Curry     : '@@@';
Apply     : '@@';
LetAssign : '@=';
/* upper lower*/



*/