1. Pascal
Winter 2010/11
Course

2. Introduction Imperative and procedural programming language
Designed: 1968/9
Published: 1970
Static and strong typing
Static binding
We will use:
FreePascal
These concepts will be explained in the lectures
Winter 2010/11
Course

3. A basic Pascal program program HelloWorld;
{ Definitions are placed here - types, variables, procedures, functions, … }
begin
WriteLn(‘Hello World!’);
{ More statements can be added here }
end.
Winter 2010/11
Course

4. A basic Pascal program Program Heading program HelloWorld;
{ Definitions are placed here - types, variables, procedures, functions, … }
begin
WriteLn(‘Hello World!’);
{ More statements can be added here }
end.
Program Heading
Winter 2010/11
Course

5. A basic Pascal program Block program HelloWorld;
{ Definitions are placed here - types, variables, procedures, functions, … }
begin
WriteLn(‘Hello World!’);
{ More statements can be added here }
end.
Block
Winter 2010/11
Course

6. A basic Pascal program Declaration Part program HelloWorld;
{ Definitions are placed here - types, variables, procedures, functions, … }
begin
WriteLn(‘Hello World!’);
{ More statements can be added here }
end.
Declaration Part
Winter 2010/11
Course

7. A basic Pascal program Statement Part program HelloWorld;
{ Definitions are placed here - types, variables, procedures, functions, … }
begin
WriteLn(‘Hello World!’);
{ More statements can be added here }
end.
Statement Part
Winter 2010/11
Course

8. Data Types Pascal has 4 primitive types:
integer, boolean, real, char
We can also create our own types:
Enumerated types:
type Color = (Red, Green, Blue, Yellow);
type MonthType = (January, February, ... ,December);
Enumerated types are comparable:
Red < Blue = true,
succ(Red) = Green,
pred(Blue) = Green,
ord(Yellow) = 3
Winter 2010/11
Course

9. Data Types - cont. Subrange types:
type Letter = ‘A’ .. ’Z’; Index = ; ColorList = Red .. Blue;
Records (Complex types like C structs):
type date = record
day : ;
month : MonthType;
year : ;
end;
Winter 2010/11
Course

10. Arrays in Pascal Pascal arrays are defined as follow:
array [<index-type>] of <element-type>
May have multiple indexes (dimensions):
array [1..5 , 2..6] of …
Example:
var A : array [1..5] of real;
var pens : array [Red..Green] of record
width : 1..3;
kind : (Regular,Bold);
end;
For col := Red to Yellow do
writeLn(pens[col].width);
!!!
Winter 2010/11
Course

11. Functions and Procedures
Pascal functions always return a value
function myFunc(…) : int;
begin …
myFunc := 13; {note how we set the value}
end;
A function that doesn’t return anything is a procedure.
procedure myProc(…);
Winter 2010/11
Course

12. A simple problem… Given a range of positive numbers:
Summarize all numbers in range that divide by 3 or 5.
Print the result.
Winter 2010/11
Course

13. Version 1
program Sum; function sumOfMatching(s, e : integer) : integer; var sum, i : integer; begin sum := 0; for i := s to e do if ( (i mod 3 = 0) or (i mod 5 = 0) ) then sum := sum + i; end; sumOfMatching := sum; WriteLn( sumOfMatching(1,1000) ); end.
Winter 2010/11
Course

14. Version 1 What if s<0? e<0? Auxiliary Function?
program Sum; function sumOfMatching(s, e : integer) : integer; var sum, i : integer; begin sum := 0; for i := s to e do if ( (i mod 3 = 0) or (i mod 5 = 0) ) then sum := sum + i; end; sumOfMatching := sum; WriteLn( sumOfMatching(1,1000) ); end.
What if s<0? e<0?
Auxiliary
Function?
Winter 2010/11
Course

15. Version 2
program Sum; type positiveInt = 1..MAXINT; function isMatching(i : integer) : boolean; begin isMatching := ((i mod 3 = 0) or (i mod 5 = 0)); end; function sumOfMatching(s, e : positiveInt) : integer; var sum, i : integer; sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; sumOfMatching := sum; begin WriteLn( sumOfMatching(1,1000) ); end.
What if s>e?
Winter 2010/11
Course

16. Version 3
program Sum; type positiveInt = 1..MAXINT; function SumOfMatching(s, e : positiveInt) : Integer; var sum, i : integer; function isMatching(i : integer) : boolean; begin isMatching := ((i mod 3 = 0) or (i mod 5 = 0)); end; sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; sumOfMatching := sum; begin WriteLn( sumOfMatching(1,1000) ); end.
Winter 2010/11
Course

17. Version 3 What is the difference? Can it be done in C/C++?
program Sum; type positiveInt = 1..MAXINT; function SumOfMatching(s, e : positiveInt) : Integer; var sum, i : integer; function isMatching(i : integer) : boolean; begin isMatching := ((i mod 3 = 0) or (i mod 5 = 0)); end; sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; sumOfMatching := sum; begin WriteLn( sumOfMatching(1,1000) ); end.
What is the difference? Can it be done in C/C++?
‘3’ and ‘5’ should be inputs / consts…
Winter 2010/11
Course

18. Version 4
program Sum; type positiveInt = 1..MAXINT; function sumOfMatching(s,e,div1,div2:positiveInt):integer; var sum, i : integer; function isMatching(i , d1, d2 : integer) : boolean; begin isMatching := ((i mod d1=0) or (i mod d2=0)); end; sum := 0; for i := s to e do begin if (isMatching(i,div1,div2)) then sum:=sum+i; sumOfMatching := sum; begin WriteLn( sumOfMatching(1,1000, 3, 5) ); end.
Winter 2010/11
Course

19. ‘div1’ and ‘div2’ are already known to nested function ‘isMatching’!
Version 4
program Sum; type positiveInt = 1..MAXINT; function sumOfMatching(s,e,div1,div2:positiveInt):integer; var sum, i : integer; function isMatching(i , d1, d2 : integer) : boolean; begin isMatching := ((i mod d1=0) or (i mod d2=0)); end; sum := 0; for i := s to e do begin if (isMatching(i,div1,div2)) then sum:=sum+i; sumOfMatching := sum; begin WriteLn( sumOfMatching(1,1000, 3, 5) ); end.
‘div1’ and ‘div2’ are already known to nested function ‘isMatching’!
Winter 2010/11
Course

20. Version 5
program Sum; type positiveInt = 1..MAXINT; function sumOfMatching(s,e,div1,div2:positiveInt):integer; var sum, i : Integer; function isMatching(i : Integer) : boolean; begin isMatching:=((i mod div1=0) or (i mod div2=0)); end; sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; sumOfMatching := sum; begin WriteLn( sumOfMatching(1,1000, 3, 5) ); end.
Winter 2010/11
Course

21. A more general solution
We can also change ‘isMatching’ to receive a matcher - a pointer to a function, as an argument, and call it with any integer→boolean function we desire.
Winter 2010/11
Course

22. Version 6
program Sum; type positiveInt = 1..MAXINT; type matcher = function ( i:integer ) : boolean; { defining a matcher } function m1( i : integer ) : boolean; begin m1 := ((i mod 7 = 0) or (i mod 13 = 0)); end; ...
Winter 2010/11
Course

23. Version 6 – cont. Notice the syntax – ‘@’
... function sumOfMatching( s, e : positiveInt ; isMatching : matcher ) : integer; var sum, i : Integer; begin for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; end; WriteLn( sumOfMatching(1, ); end.
Notice the syntax –
Winter 2010/11
Course

24. So why learn Pascal?? Still quite useful Safety Speed and Size
Mixing types leads to errors.
No type casting and no pointer arithmetic.
Speed and Size
Pascal compiler still fast.
Teaching Purposes
Shown to be easier to learn.
Less overhead and fewer ways for a student to get a program into trouble.
Winter 2010/11
Course

25. So why learn Pascal?? – cont.
Still in the market
Many small-scale freeware, shareware, and open-source programs are written in Pascal or in Delphi (“Object Pascal”).
We will use Pascal and Pascal-like languages in many examples and most likely in some of the exam questions.
So you need to know the basics of it… 
Winter 2010/11
Course