1. Pascal 234319 CourseWinter 2010/111

2. Introduction Imperative and procedural programming language Designed: 1968/9 Published: 1970 Static and strong typing Static binding We will use: – FreePascal 2.4.0 http://www.freepascal.org/download.var http://www.freepascal.org/download.var Winter 2010/11234319 Course These concepts will be explained in the lectures 2

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 2010/11234319 Course3

4. 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 2010/11234319 Course Program Heading 4

5. 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 2010/11234319 Course Block 5

6. 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 2010/11234319 Course Declaration Part 6

7. 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 2010/11234319 Course Statement Part 7

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 2010/11234319 Course8

9. Data Types - cont. – Subrange types: type Letter = ‘A’.. ’Z’; Index = 3.. 8; ColorList = Red.. Blue; – Records (Complex types like C structs): type date = record day : 1.. 31; month : MonthType; year : 1900.. 2100; end; Winter 2010/11234319 Course9

10. Arrays in Pascal Winter 2010/11234319 Course10 Pascal arrays are defined as follow: array [ ] of May have multiple indexes: array [1..5, 8..10] 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); !!!

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(…); begin … end; Winter 2010/11234319 Course11

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 2010/11234319 Course12

13. program Sum; function sumOfMatching(s, e : integer) : integer; var sum, i : integer; begin sum := 0; for i := s to e do begin if ( (i mod 3 = 0) or (i mod 5 = 0) ) then sum := sum + i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000) ); end. Version 1 Winter 2010/11234319 Course13

14. Version 1 program Sum; function sumOfMatching(s, e : integer) : integer; var sum, i : integer; begin sum := 0; for i := s to e do begin if ( (i mod 3 = 0) or (i mod 5 = 0) ) then sum := sum + i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000) ); end. What if s<0? e<0? Auxiliary Function? Winter 2010/11234319 Course14

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; begin sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000) ); end. What if s>e? Winter 2010/11234319 Course15

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; begin sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000) ); end. Winter 2010/11234319 Course16

17. 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; begin sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000) ); end. ‘3’ and ‘5’ should be inputs / consts… What is the difference? Can it be done in C/C++? Winter 2010/11234319 Course17

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; begin sum := 0; for i := s to e do begin if (isMatching(i,div1,div2)) then sum:=sum+i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000, 3, 5) ); end. Winter 2010/11234319 Course18

19. 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; begin sum := 0; for i := s to e do begin if (isMatching(i,div1,div2)) then sum:=sum+i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000, 3, 5) ); end. ‘div1’ and ‘div2’ are already known to nested function ‘isMatching’! Winter 2010/11234319 Course19

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; begin sum := 0; for i := s to e do begin if ( isMatching(i) ) then sum := sum + i; end; sumOfMatching := sum; end; begin WriteLn( sumOfMatching(1,1000, 3, 5) ); end. Winter 2010/11234319 Course20

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 2010/11234319 Course21

22. 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 2010/11234319 Course Version 6 22

23. ... 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;... end; begin WriteLn( sumOfMatching(1, 1000, @m1) ); end. Winter 2010/11234319 Course Version 6 – cont. Notice the syntax – ‘@’ 23