COP2213 Lecture Handout 10/6/99

{This is a test program to illustrate pass by value in functions and procedures.}

program ProcTest;

procedure X(a,b,c: integer);
begin
  a := b + c;
  c := a + b;
  b := c - b;
  writeln('In X: a = ',a,' b = ',b,' c = ',c);
end;

function Y(a,b,c: integer): integer;
begin
  a := 2*a;
  b := 2*b;
  c := 2*c;
  writeln('In Y: a = ',a,' b = ',b,' c = ',c);
  Y := a + b + c;
end;

var a,b,c : integer;

begin
  a := 1;
  b := 2;
  c := 3;
  X(b,c,a);
  writeln('In Main: a = ',a,' b = ',b,' c = ',c);
  X(2*a-2, 3*c+b, b-a);
  writeln('In Main: a = ',a,' b = ',b,' c = ',c);
  b := Y(a+b,b+c,a+c);
  writeln('In Main: a = ',a,' b = ',b,' c = ',c);
end.



















{This is a test program to illustrate pass by reference.}
program ProcTest;

procedure X(var a,b: integer; c: integer);
begin
  a := b + c;
  c := a + b;
  b := c - b;
  writeln('In X: a = ',a,' b = ',b,' c = ',c);
end;

function Y(var a,b,c: integer): integer;
begin
  a := 2*a;
  b := 2*b;
  c := 2*c;
  writeln('In Y: a = ',a,' b = ',b,' c = ',c);
  Y := a + b + c;
end;

var a,b,c : integer;

begin
  writeln;
  a := 1;
  b := 2;
  c := 3;
  X(b,c,a+1);
  writeln('In Main: a = ',a,' b = ',b,' c = ',c);
  X(c,b,a);
  writeln('In Main: a = ',a,' b = ',b,' c = ',c);
  b := Y(a,b,c);
  writeln('In Main: a = ',a,' b = ',b,' c = ',c);
end.