1. (c)opyright Brent M. Dingle 2001
Strings
Brent M. Dingle Texas A&M University
Chapter 9 – Section 3
(and some from Mastering Turbo Pascal 5.5, 3rd Edition by Tom Swan)
Fall 2001
(c)opyright Brent M. Dingle 2001

2. (c)opyright Brent M. Dingle 2001
Strings
We have actually been using strings for some time now.
So you should be familiar with how they work.
A couple things you might not have discovered yet:
How to index into a string
How to pass a string of declared size to a procedure or function.
Fall 2001
(c)opyright Brent M. Dingle 2001

3. (c)opyright Brent M. Dingle 2001
Indexing into a string
Suppose we had the following:
VAR
name : string[30]; :
name := ‘Lilly Flower’;
Now how might we determine what the first letter of name is? (say we were doing something alphabetically with names)
Any guesses?
Fall 2001
(c)opyright Brent M. Dingle 2001

4. Indexing into a string (cont)
As it turns out strings are ‘special’ arrays in Pascal. So we can do some neat tricks with them by treating them as arrays.
So the first character of name can be found by: Writeln(name[1]);
Notice this means strings start their indexing at ONE.
What do you think the value of name[5] is?
Fall 2001
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5. (c)opyright Brent M. Dingle 2001
Name[k] values
For reference:
name[1] = ‘L’
name[2] = ‘i’
name[3] = ‘l’
name[4] = ‘l’
name[5] = ‘y’
name[6] = ‘ ‘ that’s a space character
name[7] = ‘F’
name[8] = ‘l’
: :
name[12] = ‘r’
Fall 2001
(c)opyright Brent M. Dingle 2001

6. (c)opyright Brent M. Dingle 2001
Strings to procedures
As you undoubtedly have discovered from the homework, the procedure declaration:
procedure GetName(var name : string[40]);
Fails to compile.
Previously the only fix was to just say:
procedure GetName(var name : string);
Fall 2001
(c)opyright Brent M. Dingle 2001

7. Strings to procs (cont)
However, now we have learned that we can use TYPEs.
So declare the type:
TYPE
string40 = string[40];
And use the declaration:
procedure GetName(var name : string40);
Fall 2001
(c)opyright Brent M. Dingle 2001

8. String and array passing
Notice similar difficulties occur when we try to pass arrays:
procedure La(var grades : array [1..5] of real);
Does NOT work.
But with items declared as below:
TYPE
GRADE_ARY = array [1..5] of real; :
procedure La(var grades : GRADE_ARY);
It does work and all is happy time.
Fall 2001
(c)opyright Brent M. Dingle 2001

9. (c)opyright Brent M. Dingle 2001
String Functions
Some useful string functions in Turbo Pascal (know them, use them, lov… well, just know and use them =)
concat(str1, str2, …, str[n]);
pos(find_me, in_this);
delete(from_me, start_pos, num_chars);
insert(new_str, into_me, start_pos);
length(of_me);
copy(from_me, start_pos, num_chars);
upcase(str);
These are all explained well enough in the book.
Fall 2001
(c)opyright Brent M. Dingle 2001

10. (c)opyright Brent M. Dingle 2001
Challenge
Create a program that will read text from a file and replace all the occurrences of the words ‘he’ and ‘she’ with the word ‘it’.
The output should be a NEW text file with the changes made.
Fall 2001
(c)opyright Brent M. Dingle 2001

11. Suggested Probs (no grade)
page 364 19
Programming pages 369 – 372
22 – do it first without arrays, then with them, then up the number of integers to 50 (instead of just 10).
23 – see if you can use an enumerated data type to index into your 5 element array.
26, 29, 31
Fall 2001
(c)opyright Brent M. Dingle 2001

12. (c)opyright Brent M. Dingle 2001
End Strings
Chapter 9.3
And thus ends Chapter 9
Fall 2001
(c)opyright Brent M. Dingle 2001