如何正确将求数组众数的C++代码转为GnuCOBOL并修复语法错误

核心语法错误就是每个COBOL程序结束后必须显式声明END PROGRAM 对应程序ID，你编写的三个程序（Main、READDATA、MODE）都没有加结束声明，编译器会认为所有代码都属于第一个Main程序，读到READDATA的WORKING-STORAGE段时自然不符合Main程序的语法结构，就抛出了你看到的报错。

• 子程序接收的传入参数不能定义在WORKING-STORAGE段，需要定义在LINKAGE SECTION段，且PROCEDURE DIVISION需要声明接收的参数
• READDATA子程序的循环逻辑错误：PERFORM VARYING已经会自动迭代I变量，循环内执行SET I TO 1会导致死循环
• MODE子程序的比较逻辑错误：判断元素相等的条件写成了array(I) = array(I)，永远返回真，和C++逻辑不符，应该改为val(I) = val(J)
• 变量定义不规范：数值类型变量应该用PIC 9(1)定义，原代码混用了X(1)、错误的PIC(1)写法，且循环变量I、J没有提前定义
• 众数统计逻辑位置错误：max值更新应该放在内层J循环内，和C++逻辑对齐

IDENTIFICATION DIVISION.
PROGRAM-ID. Main.
DATA DIVISION.
WORKING-STORAGE SECTION.
    01 array.
        05 val PIC 9(1) OCCURS 5 TIMES.
PROCEDURE DIVISION.
    CALL 'READDATA' USING array.
    STOP RUN.
END PROGRAM Main.

*> readData: 从用户输入填充数组
IDENTIFICATION DIVISION.
PROGRAM-ID. READDATA.
DATA DIVISION.
LINKAGE SECTION.
    01 array.
        05 val PIC 9(1) OCCURS 5 TIMES.
WORKING-STORAGE SECTION.
    01 I PIC 9(1) VALUE 1.
PROCEDURE DIVISION USING array.
    PERFORM VARYING I FROM 1 BY 1
        UNTIL I > 5
        ACCEPT val(I) FROM SYSIN
    END-PERFORM.
    CALL 'MODE' USING array.
    EXIT PROGRAM.
END PROGRAM READDATA.

*> mode: 计算数组众数并输出
IDENTIFICATION DIVISION.
PROGRAM-ID. MODE.
DATA DIVISION.
LINKAGE SECTION.
    01 array.
        05 val PIC 9(1) OCCURS 5 TIMES.
WORKING-STORAGE SECTION.
    01 I PIC 9(1) VALUE 1.
    01 J PIC 9(1) VALUE 1.
    01 maxv PIC 9(1) VALUE 0.
    01 counter PIC 9(1) VALUE 0.
    01 num PIC 9(1) VALUE 0.
PROCEDURE DIVISION USING array.
    PERFORM VARYING I FROM 1 BY 1
        UNTIL I > 5
            MOVE 0 TO counter
            PERFORM VARYING J FROM 1 BY 1
                UNTIL J > 5
                IF val(I) = val(J) THEN
                    ADD 1 TO counter
                END-IF
                IF maxv < counter THEN
                    MOVE counter TO maxv
                    MOVE val(I) TO num
                END-IF
            END-PERFORM
    END-PERFORM.
    DISPLAY "Mode: " num.
    EXIT PROGRAM.
END PROGRAM MODE.

输入示例数组的5个元素：1、2、2、1、1，程序会输出Mode: 1，和C++代码运行结果一致。

内容的提问来源于stack exchange，提问作者Darthvader