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Learn the Language

Lesson 5: Structs and Arrays

Basics of Arrays

  • An array is basically a collection of multiple values of the same type. So if you have multiple values but you don’t know how many, you can use an array and you can access that using a numeric index.
  • Arrays are dynamically sized, so don’t have to specify upfront how many items you have.
  • You can use static arrays, so when you define a size upfront. Useful for low-level purposes.
  • An array can met multi-dimensional.

Basics of Structs

  • A struct is custom defined data type, you define multiple variables that together from a struct.
  • Each member is of a specific type, a member can be an integer or string or array of strings.
  • A struct can also be another struct. You can have structs within your structs, or even an array of structs.

Demonstration 

  1. Click PROJECTS NEW > PROJECT > BASIC PROJECT > OK
  2. Name your project, in this case: Arrays > OK
  3. Clear out the code it generated and replace with:
    Use DfAllEnt.pkg
  4. Create new procedure

5. Define Array, in this case we are going to make an array of strings. We are going to fill the array with values, names in this case.

6. Loop over these items, by declaring an integer.

7. Note: At line 12 the expression SizeOfArray is used to retrieve the size of a dynamic array, so in this case 4. But because arrays are 0 based, we have to subtract 1, so it will only run till number 3.

8. To make sure that you can see a result, add an info box at the end.

9. Click RUN (F5), now you can see it ran through all the names and it shows and shows an info box that says “Done..”.

10. Place a breakpoint > click RUN (F5)

11. In the Locals window you can now see that “aNames” has an array with 0 elements.

12. As soon as we execute this line, we get an array of 1 element. If we execute the next, 2 elements. Etc. You can also expand the “anames” tree in Locals to see all the separate elements listed.

13. Continue to step through the program until the final info box comes up.

14. Add the following line of code to your application:

Move (SortArray(aNames))

15. (SortArray(aNames)) Returns the sorted array.

16. Place a breakpoint at line 12

17. Click RUN (F5)

18. Take a look at aNames in the locals panel, if you press F10 (Step Over) you see that the order of the array has now changed, it’s now alphabetical order.

19. Click RUN (F5) to run the rest of the program, the output in the output window will also be displayed in alphabetical order.

20. Click OK to close

21. Another function used with arrays is the search function. Add the following code to your application.

22. Click RUN (F5)

23. Note: The output window shows it has found Nick at position 2. He is the third item on the list, but because arrays are zero based, he becomes number 2.