< WE Language grammar >
※ 아래 표기에서 단어 뒷편의 '~' 표시는 생략 가능함을 의미한다.
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expression:
        primary
        - expression
        ! expression
        ~ expression
        ++ lvalue
        -- lvalue
        lvalue ++
        lvalue --
        expression binop expression
        lvalue asgnop expression
        expression , expression

primary:
        identifier
        constant
        string
        ( expression )
        identifier ( expression-list~ )
        identifier [ expression-list ]

lvalue:
        identifier
        identifier [ expression ]

binop:
        ,       ~      ||      &&      |       ^       &       ==      !=
        >       >=     <       <=      <<      >>      +       -       *
        /       %      **

asgnop:
        =       ~=     +=      -=      *=      /=      %=      |=      ^=
        &=      <<=    >>=     **=

declaration:
        type-specifier init-declarator-list;

type-specifier:
        char
        int
        long
        float
        double
        string
        free

init-declarator-list:
        init-declarator
        init-declarator, init-declarator-list

init-declarator:
        declarator initializer~

declarator-list:
        declarator
        declarator, declarator-list

declarator:
        identifier
        declarator [ constant-expression ]

initializer:
        = expression

compound-statement:
        { declaration-list~ statement-list~ }

declaration-list:
        declaration
        declaration declaration-list

statement-list:
        statement
        statement statement-list

statement:
        compound-statement
        expression;
        if (expression) statement
        if (expression) statement else statement
        while (expression) statement
        do statement while expession;
        for (expression-1~; expression-2~; expression-3~) statement
        break;
        continue;
        return;
        return expression;
        vlock declarator-list;
        vunlock declarator-list;
        vfree declarator-list;
        goto identifier;
        identifier : statement
        ;
program:
        function-definition
        function-definition program

function-definition:
        function type-specifier~ function-declarator function-body

function-declarator:
        declarator ( parameter-list~ )

parameter-list:
        identifier
        identifier , parameter-list

function-body:
        type-decl-list function-statement

function-statement:
        { declaration-list~ statement-list }

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