具有功能的分流码算法

时间：2014-09-30 19:37:12

标签： function vbscript interpreter shunting-yard

我的第一篇文章：）

我看到有很多关于调车场算法的问题但是我 希望仍然有论坛成员有兴趣帮助我解决这个算法的另一个问题。

我确实搜索了其他帖子，看看我的答案是否已经回答，我在其他论坛和互联网上进行了一些研究：

http://stackoverflow.com/questions/16877546/modifying-the-shunting-yard-algorithm-c
http://www.computerhope.com/forum/index.php?topic=146535.0
http://en.wikipedia.org/wiki/Shunting-yard_algorithm
http://www.autoitscript.com/forum/topic/164627-shunting-yard-with-functions/

我的代码是用vb脚本编写的，因为我喜欢它的简单性而且我不懂java或类似的语言..

我的问题：

目前该算法允许错误使用＆＃34;（＆＃34;和＆＃34;）＆＃34; 例如：函数（（10,20，）30）是允许的，但显然不是调用函数的正确方法..

我也不确定我的代码是否写得正确，维基百科的伪代码是我的参考，但不是很清楚：（

我还计划用if-else语句和嵌套循环和东西来扩展它，因为主要目标是在类似语言的vb中编写某种解释器作为学习项目：）

我的代码[编辑]：

SET PRECEDENCE = CREATEOBJECT("SCRIPTING.DICTIONARY")
WITH PRECEDENCE
    .ADD "^",3
    .ADD "*",2
    .ADD "/",2
    .ADD "%",2
    .ADD "+",1
    .ADD "-",1
    .ADD "FUNCTION",0
    .ADD "(",0
    .ADD ",",0
    .ADD ")",0
END WITH

'#############################################################################
tokenArray = split("FUNCTION ( ( A , B ) , C )")
msgbox SHUNTINGYARD(tokenArray)
'#############################################################################

FUNCTION SHUNTINGYARD(INPUT)

    TOKEN_QUEUE = ARRAY()
    TOKEN_STACK = ARRAY()

    FOR TOKEN_NUMBER = 0 TO UBOUND(INPUT)
        SELECT CASE INPUT(TOKEN_NUMBER)

            CASE "("
                CALL PUSH(INPUT(TOKEN_NUMBER), TOKEN_STACK)

            CASE ")"
                DO WHILE NOT( PRECEDENCE( PEEK(TOKEN_STACK) ) = 0 )
                    CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
                    IF STACKISEMPTY(TOKEN_STACK) THEN CALL ERRORS("Can't find a matching ""("".", TRUE)
                LOOP

                IF PEEK(TOKEN_STACK) = "FUNCTION" THEN
                    DISCARD = POP(TOKEN_STACK)
                    CALL PUSH("@", TOKEN_QUEUE)
                ELSE
                    DISCARD = POP(TOKEN_STACK)
                END IF

            CASE ","
                DO WHILE NOT( PRECEDENCE( PEEK(TOKEN_STACK) ) = 0 )
                    CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
                    IF STACKISEMPTY(TOKEN_STACK) THEN CALL ERRORS("Can't find a matching function ""("".", TRUE)
                LOOP

            CASE "+","-","*","/","^","%"
                TOKEN_A = INPUT(TOKEN_NUMBER)
                DO WHILE ISOPERATOR(PEEK(TOKEN_STACK))
                    TOKEN_B = PEEK(TOKEN_STACK)
                    IF (ASSOCIATIVITY(TOKEN_B) = "left" AND PRECEDENCE(TOKEN_A) = PRECEDENCE(TOKEN_B)) OR (PRECEDENCE(TOKEN_A) < PRECEDENCE(TOKEN_B)) THEN
                        CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
                    ELSE
                        EXIT DO
                    END IF
                LOOP
                CALL PUSH(TOKEN_A, TOKEN_STACK)

            CASE ELSE
                CALL PUSH(INPUT(TOKEN_NUMBER), TOKEN_QUEUE)

        END SELECT
    NEXT

    FOR ITEMCOUNT = 0 TO UBOUND(TOKEN_STACK)
        IF PEEK(TOKEN_STACK) = "(" THEN CALL ERRORS("Can't find a matching "")"".", TRUE)'(
        CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
    NEXT

    SHUNTINGYARD = JOIN(TOKEN_QUEUE,"|")

END FUNCTION

'#############################################################################

FUNCTION ASSOCIATIVITY(ASSOC)
    SELECT CASE LCASE(ASSOC)
        CASE "^","\"
            ASSOCIATIVITY = "right"
        CASE ELSE
            ASSOCIATIVITY = "left"
    END SELECT
END FUNCTION

FUNCTION ISOPERATOR(ITEM)
    ISOPERATOR = LEN(ITEM) = 1 AND INSTR("+-*/%^",ITEM)
END FUNCTION

SUB PUSH(ITEM,BYREF STACK)
    IF UBOUND(STACK) > -1 THEN
        REDIM PRESERVE STACK(UBOUND(STACK) + 1)
        STACK(UBOUND(STACK)) = ITEM
    ELSE
        STACK = ARRAY(ITEM)
    END IF
END SUB

FUNCTION POP(BYREF STACK)
    IF UBOUND(STACK) > -1 THEN
        POP = STACK(UBOUND(STACK))
        REDIM PRESERVE STACK(UBOUND(STACK) - 1)
    END IF
END FUNCTION

FUNCTION STACKISEMPTY(STACK)
    IF UBOUND(STACK) > -1 THEN
        STACKISEMPTY = FALSE
    ELSE
        STACKISEMPTY = TRUE
    END IF
END FUNCTION

FUNCTION PEEK(STACK)
    IF UBOUND(STACK) > -1 THEN
        PEEK = STACK(UBOUND(STACK))
    END IF
END FUNCTION

1 个答案:

答案 0 :(得分：3)

你可以对待＆＃34; FUN＆＃34;，＆＃34;（＆＃34;，＆＃34;）＆＃34;，＆＃34;，＆＃34;与其他运算符类似，可以推送到TOKEN_STACK。 （因为简洁，我将FUNCTION缩短为FUN）。 ＆＃34;乐趣＆＃34;，＆＃34;（＆＃34;，＆＃34;）＆＃34;，＆＃34;，＆＃34;优先级低于＆＃34; +＆＃34;所以优先表看起来像

^                    4
*  /  %              3
+  -                 2
( ) ,   FUN          1

考虑解析1 + FUN（2 * 3）时会发生什么

Remaining Input     Stack             Output
1+FUN(2*3)                          
+FUN(2*3)                           1
FUN(2*3)          +                 1
(2*3)             +  FUN            1
2*3)              +  FUN  (         1
*3)               +  FUN  (         1  2
3)                +  FUN  (  *      1  2
)                 +  FUN  (  *      1  2  3
                  +  FUN  (  *  )   1  2  3          Note 1
                  +  FUN  ( )       1  2  3  *       Note 2
                  +                 1  2  3  * FUN() 
                                    1  2  3  * FUN() +

输出令牌＆＃34; FUN（）＆＃34;代表功能评估。

注1：当我们试图推动＆＃34;）＆＃34;在堆栈中，所有具有更高优先级的运算符都从堆栈中取出并移动到输出。

注2：当堆栈末尾的项目匹配＆＃34;（＆＃34;，然后从堆栈中删除。有两种情况需要处理，简单匹配括号，如1 +（2 * 3） 或者如果在＆＃34;（＆＃34;在堆栈上）之前有一个函数令牌。在这种情况下，从堆栈弹出FUN并向输出添加一个函数评估令牌。

＆＃34;＆＃34;将以类似的方式对待＆＃34;）＆＃34;导致具有更高优先级的运算符被弹出。但它不会导致输出功能评估。你需要一些方法来记录一个函数有多少个参数。

在我的代码中，我使用基于递归的算法。解析算法可以递归调用，并给出一个停止令牌。遇到stop-token时，它会退出递归。当遇到一个函数时，它调用递归等待＆＃34;，＆＃34;或＆＃34;）＆＃34;。

我设法使用cscript命令行程序运行iut。我还在Wscript.Echo中添加了一些调试代码。

查看TOKEN_STACK，你没有将FUNCTION令牌添加到堆栈中，所以当你搜索它时它不存在。

添加             案例＆＃34;功能＆＃34;                 CALL PUSH（INPUT（TOKEN_NUMBER），TOKEN_STACK）

似乎给了正确的答案。虽然我不确定当你匹配第一个结束括号时应该发生什么。它的输入也非常错误，例如＆＃34; E + FUNCTION（（A，B），C）+ F＆＃34;。

SET PRECEDENCE = CREATEOBJECT("SCRIPTING.DICTIONARY")
WITH PRECEDENCE
    .ADD "^",3
    .ADD "*",2
    .ADD "/",2
    .ADD "%",2
    .ADD "+",1
    .ADD "-",1
    .ADD "FUNCTION",0
    .ADD "(",0
    .ADD ",",0
    .ADD ")",0
END WITH

Wscript.Echo "Start"

'#############################################################################
tokenArray = split("FUNCTION ( ( A , B ) , C )")
'#tokenArray = split("A + B * C")


Wscript.Echo "Result " + SHUNTINGYARD(tokenArray)
'#############################################################################

FUNCTION SHUNTINGYARD(INPUT)

    TOKEN_QUEUE = ARRAY()
    TOKEN_STACK = ARRAY()

    FOR TOKEN_NUMBER = 0 TO UBOUND(INPUT)
    Wscript.Echo "Token " + INPUT(TOKEN_NUMBER)
    Wscript.Echo "Stack " + JOIN(TOKEN_STACK,"|")

        SELECT CASE INPUT(TOKEN_NUMBER)

            CASE "("
                CALL PUSH(INPUT(TOKEN_NUMBER), TOKEN_STACK)

            CASE ")"

                DO WHILE NOT( PRECEDENCE( PEEK(TOKEN_STACK) ) = 0 )

                    CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
                    IF STACKISEMPTY(TOKEN_STACK) THEN CALL ERRORS("Can't find a matching ""("".", TRUE)
                LOOP

                IF PEEK(TOKEN_STACK) = "FUNCTION" THEN
                    DISCARD = POP(TOKEN_STACK)
                    CALL PUSH("@", TOKEN_QUEUE)
                ELSE
                    DISCARD = POP(TOKEN_STACK)
                END IF

            CASE ","
                DO WHILE NOT( PRECEDENCE( PEEK(TOKEN_STACK) ) = 0 )
                    CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
                    IF STACKISEMPTY(TOKEN_STACK) THEN CALL ERRORS("Can't find a matching function ""("".", TRUE)
                LOOP

            CASE "+","-","*","/","^","%"
                TOKEN_A = INPUT(TOKEN_NUMBER)
                DO WHILE ISOPERATOR(PEEK(TOKEN_STACK))
                    TOKEN_B = PEEK(TOKEN_STACK)
                    IF (ASSOCIATIVITY(TOKEN_B) = "left" AND PRECEDENCE(TOKEN_A) = PRECEDENCE(TOKEN_B)) OR (PRECEDENCE(TOKEN_A) < PRECEDENCE(TOKEN_B)) THEN
                        CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
                    ELSE
                        EXIT DO
                    END IF
                LOOP
                CALL PUSH(TOKEN_A, TOKEN_STACK)

            CASE "FUNCTION"
                CALL PUSH(INPUT(TOKEN_NUMBER), TOKEN_STACK)

            CASE ELSE
                CALL PUSH(INPUT(TOKEN_NUMBER), TOKEN_QUEUE)

        END SELECT
    NEXT

    FOR ITEMCOUNT = 0 TO UBOUND(TOKEN_STACK)
        IF PEEK(TOKEN_STACK) = "(" THEN CALL ERRORS("Can't find a matching "")"".", TRUE)'(
        CALL PUSH(POP(TOKEN_STACK), TOKEN_QUEUE)
    NEXT

    SHUNTINGYARD = JOIN(TOKEN_QUEUE,"|")

END FUNCTION

'#############################################################################

FUNCTION ASSOCIATIVITY(ASSOC)
    SELECT CASE LCASE(ASSOC)
        CASE "^","\"
            ASSOCIATIVITY = "right"
        CASE ELSE
            ASSOCIATIVITY = "left"
    END SELECT
END FUNCTION

FUNCTION ISOPERATOR(ITEM)
    ISOPERATOR = LEN(ITEM) = 1 AND INSTR("+-*/%^",ITEM)
END FUNCTION

SUB PUSH(ITEM,BYREF STACK)
    IF UBOUND(STACK) > -1 THEN
        REDIM PRESERVE STACK(UBOUND(STACK) + 1)
        STACK(UBOUND(STACK)) = ITEM
    ELSE
        STACK = ARRAY(ITEM)
    END IF
END SUB

FUNCTION POP(BYREF STACK)
    IF UBOUND(STACK) > -1 THEN
        POP = STACK(UBOUND(STACK))
        REDIM PRESERVE STACK(UBOUND(STACK) - 1)
    END IF
END FUNCTION

FUNCTION STACKISEMPTY(STACK)
    IF UBOUND(STACK) > -1 THEN
        STACKISEMPTY = FALSE
    ELSE
        STACKISEMPTY = TRUE
    END IF
END FUNCTION

FUNCTION PEEK(STACK)
    IF UBOUND(STACK) > -1 THEN
        PEEK = STACK(UBOUND(STACK))
    END IF
END FUNCTION
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