ITEC 320

1. ITEC 320 Lecture 6 More on arrays / Strings

2. Review • Scope • Exceptions • Arrays • Dynamic arrays • How? • Typed and anonymous

3. Issue • Named type required for passing to functions / procedures What is values 1? Can’t duplicate when passing to a function. procedure demo is values1: array (1 .. 50) of integer; values2: array (1 .. 50) of integer; begin values1 := (2 => 4, 4 => 16, 5 => 25, 3 => 9, others => 0); values2 := (others => 0); end demo;

4. Comparisons type Myarray is array (1 .. 3) of Integer; a, b: Myarray; ... a := (10, 20, 30); b := (others => 0); if a = b then ... b := a; if a = b then ... Note: types must be the same Checks each element! Assignment works element by element Is this shallow or deep copying?

5. Java • Behavior • Java references • Ada values int[] a = {10, 20, 30}; int[] b = {0, 0, 0}; if (a == b) ... a = b; if (a == b) ...

6. Attributes • 'first • 'last • 'range • 'length • Why is it important to know these?

7. Slices • Portions of the whole • What are the advantages / disadvantages? • How would you do this in Java? s: String := "Hi Mom!"); put(s(3 .. 5) & "?"); s(4) := 'T'; put(s); s(4 .. 6) := "Bob"; put(s); s(4 .. 4) := "R"; put(s);

8. Considerations • Sending a slice to a function / procedure • Can it be a constrained array? • What happens when you assign slices to each other? • Dynamic slice bounds (not hard coded)

9. Example declare s: String := "Hi Mom!"; begin put_line(s(4..7) & s(1..2)); and declare s: String := "Hi Mom!"; begin put_line(s(4..7) & s(3..3) & s(1..2)); put_line(s(4..7) & s(3) & s(1..2));

10. String’s • What do you remember about them? • Declaration? • Input? • Output?

11. Code • What is the difference between s: String := “Hello World”; And s2: String(1..15);

12. Issues: types must match sizes have to match Modification s: String := "Hi World"; begin put(s’first); put(s’last); s(4) := 'T'; put_line(s); s(4 .. 6) := "Ron"; put_line(s); s := ”Bye world"; put_line(s);

13. Modification(2) • Combinations s: String := "HiMom!"; u: String(1 .. 10); ... -- s := u; -- Compileerror -- u := s; -- Compileerror s := "HiBob!"; -- Okay -- s := "HiBilly-Bob!"; -- Compileerror -- s := s & "!"; -- Compileerror u = s & "!!!";

14. Loops • Why access character by character? for i in 1 .. s'length loop for i in s'first .. s'last loop for i in s'range loop

15. Input • Common usage s: String(1..10); len: Natural begin while not end_of_file loop get_line(s, len); put_line(s(1..len)); end loop;

16. Java • Reference versus value • Why do you think ADA is focused on values? String s; String t = "Mama!"; System.out.println(s); s = "today"; s = t;

17. Declare • Want to resize a String? • Use same syntax as arrays get(size); declare s3: String(1..size); begin get_line(s3, size);

18. Differences • What is the difference between put(v(1 .. len)); put(v);

19. Power tools • Unbounded strings (Like java) with Ada.Strings.Unbounded; use Ada.Strings.Unbounded; with Ada.Strings.Unbounded_Text_IO; use Ada.Strings.Unbounded_Text_IO; procedure showUnboundedis s: Unbounded_String := "first"; begin s := "different"; s := s & "!!"; put_line(s); -- different!! end showUnbounded

20. Issues • Stack versus heap • Assignment with Ada.Strings.Unbounded; use Ada.Strings.Unbounded; with Ada.Strings.Unbounded_Text_IO; use Ada.Strings.Unbounded_Text_IO; ... s: Unbounded_String := "first"; t: Unbounded_String := s; ... s := s & "!!"; put_line(s); -- first!! put_line(t) -- first;

21. Strength/Weakness • Fixed length • Unconstrained • Unbounded type string is array (Positive range) <> of Character

22. Summary • Arrays • Dynamic • Copying