Pascal Programming: Week 6 Notes       


Evaluating Expressions
         Previous Example:
			IF (Value <> 0) AND (Answer DIV Value >= 20) THEN
				Writeln(' Incorrect');
	        Fix:
 			IF (Value <> 0) THEN
			     IF (Answer DIV Value >= 20) THEN
				Writeln(' Incorrect');
	
           a:= sqr(b) * h - c + b;
          b:=  a + c * b;
          c:= b - h * h;
          h:= h - h;
          b:= b - c * TRUNC(e);
          c:= c DIV ROUND(e);
          h:= h MOD ROUND(e);

          IF (b > c) OR (b < h) AND (h < a) THEN  {do something}

          f:= f / e * 3.5 + 2.0;
          x:= x + e + x * x;
          e:= e / 4.0 * 2.1 + 1.7;

         	
Functions

	Pre-defined:  SQR(), SQRT(), TRUNC(), ROUND(), and others
	User-defined: CUBE() example

		FUNCTION Cube(x: integer): integer;
BEGIN
			     Cube:= x*x*x;
			END;  {Cube}

			FUNCTION Factorial(x: integer):integer;
VAR
     					i,temp: integer;
BEGIN
     					temp:= x;
    					FOR i:= x DOWNTO 2 DO
         					BEGIN
              						temp:= temp * (x-1);
              						x:=x-1;
         					END;
     					Factorial:= temp;
END;  {factorial}

	Functions are expressions 
	Written like a procedure but it returns a value

FUNCTION Factorial(x: longint):longint;
VAR
     temp: longint;
     i:    integer;

BEGIN
     temp:= x;
     CASE temp OF
         0:     Factorial:= 1;
         1:     Factorial:= 1;
         ELSE
	     BEGIN
     		FOR i:= x DOWNTO 2 DO
         		BEGIN
           		   temp:= temp * (x-1);
      		           x:=x-1;
         		END;  {for loop}
     		Factorial:= temp;
                END;  {else clause}
             END; {case statement}
 END; {function factorial}


Arrays
	One-Dimensional Array Declaration
	Usage of arrays
	Example:
		TYPE
			Days = (mon, tues, wed, thu, fri, sat, sun);
			SmArray = Array[1..5] of Days;
		VAR
			Index: Integer;
			List: Array[1..100] of Integer;
			Week: Array[1..7] of Days;
			WeekDays: SmArray;

		BEGIN {program}
			Writeln('Enter in the last seven days you worked');

			FOR i:= 1..7 DO Readln(Week[i]);
			Write('The listing of days worked is ');
			WHILE I > 0 DO	 
BEGIN
Write(Week[i]);
i:= I-1;
					END;  {while}
			Writeln;
		END.     {program}




User-Defined Types
	Overview of Type Declaration
	Example:
			CONST
				Noon = 12.00;
		TYPE
			Money =  Real;
			Time = Real;
			Name = String(10);
			Grade = 'A' .. 'F';
			Score = 0..100;
			PosInt = 0..maxint;
			Days = (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
		VAR
			PayDue: Money;

		PROCEDURE GetPayDue (VAR Pay: Money, Rate: Real);
			BEGIN
				{do something}
			END;     {GetPayDue}

More Number Types in Turbo Pascal pg. 558
	shortint		-128..127
	interger		-32768..32767
	longint		-2147483648..2147483647
	byte		0..255
	word		0..65535

	real		2.9*10-39 .. 1.7*1038
	single 		1.5*10-45 .. 3.4*1038
	double		5.0*10-324 .. 1.7*10308
	extended	3.4*10-4932 .. 1.1*104932

	Must set E and N compiler directive: {$N+,E+}


Units
	Overview of Unit Declaration
	Interface Part
		Procedure Heading and Documentation
	Implementation Part
		Procedure Heading and Body
	Initialization Part
		Private Variable Initialization
	Example:  Chapter 8  pg.  276-305