Slices in COBOL

COBOL doesn’t have a direct equivalent to slices, but we can use tables (arrays) to demonstrate similar concepts. Here’s an example that showcases some of the operations we can perform with tables in COBOL:

IDENTIFICATION DIVISION.
PROGRAM-ID. TABLE-OPERATIONS.

ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.

DATA DIVISION.
FILE SECTION.

WORKING-STORAGE SECTION.
01 WS-TABLE.
   05 WS-ELEMENT PIC X(1) OCCURS 10 TIMES.
01 WS-TABLE-2.
   05 WS-ELEMENT-2 PIC X(1) OCCURS 10 TIMES.
01 WS-INDEX PIC 9(2).
01 WS-TEMP PIC X(1).

PROCEDURE DIVISION.
MAIN-PROCEDURE.
    DISPLAY "Initializing table..."
    MOVE "ABCDEFGHIJ" TO WS-TABLE
    DISPLAY "Table contents: " WS-TABLE

    DISPLAY "Accessing elements..."
    DISPLAY "First element: " WS-ELEMENT(1)
    DISPLAY "Third element: " WS-ELEMENT(3)

    DISPLAY "Modifying elements..."
    MOVE "X" TO WS-ELEMENT(2)
    MOVE "Y" TO WS-ELEMENT(4)
    DISPLAY "Modified table: " WS-TABLE

    DISPLAY "Copying table..."
    MOVE WS-TABLE TO WS-TABLE-2
    DISPLAY "Copied table: " WS-TABLE-2

    DISPLAY "Slicing (sort of)..."
    DISPLAY "Elements 3-5: " WS-ELEMENT(3) WS-ELEMENT(4) WS-ELEMENT(5)

    DISPLAY "Reversing table..."
    PERFORM VARYING WS-INDEX FROM 1 BY 1 UNTIL WS-INDEX > 5
        MOVE WS-ELEMENT(WS-INDEX) TO WS-TEMP
        MOVE WS-ELEMENT(11 - WS-INDEX) TO WS-ELEMENT(WS-INDEX)
        MOVE WS-TEMP TO WS-ELEMENT(11 - WS-INDEX)
    END-PERFORM
    DISPLAY "Reversed table: " WS-TABLE

    STOP RUN.

This COBOL program demonstrates some operations that are similar to what we can do with slices in other languages:

1. We define two tables (arrays) WS-TABLE and WS-TABLE-2, each containing 10 elements.

2. We initialize WS-TABLE with a string of characters.

3. We access individual elements of the table.

4. We modify specific elements of the table.

5. We copy the entire table to another table.

6. We display a “slice” of the table (although in COBOL, this is just accessing specific elements).

7. Finally, we reverse the table to demonstrate a more complex operation.

While COBOL doesn’t have the flexibility of slices in more modern languages, tables in COBOL can be used to store and manipulate collections of data in a similar manner.

To run this COBOL program, you would typically compile it and then execute the compiled program. The exact commands depend on your COBOL compiler, but it might look something like this:

$ cobc -x table-operations.cob
$ ./table-operations

This will compile the COBOL source code into an executable and then run it, displaying the results of our table operations.

COBOL’s approach to data structures is quite different from more modern languages, reflecting its origins in business data processing. While it may seem limited compared to the slice operations in other languages, COBOL’s table handling can be very efficient for certain types of data processing tasks.