Pascal基础(二) 数据类型与控制流程(续)

命令行编译

如果没有使用IDE,可以使用命令行来编译,最简单的用法就是
fpc main.pas,具体用法可以fpc -h来查看.另外可以使用fpc -al -Amasm main.ps来生成汇编文件,里面把pas源码作为了汇编代码的注释,可是对照参考.

结构类型举例

枚举

type Color = (Red,Green,Blue);

子界

var age:0..120;
或者使用枚举作子界的起始
type Month=(Jan,Feb,Mar,Apr,May);
type Spring = Jan..Mar;

数组

type
   array-identifier = array[index-type] of element-type;

type vector = array [0..24] of integer;
type temp = array[-10..50] of real;
type color = (Red,Blue,Green,Silver);
var a:vector;b:temp;c:color;d:array [1..10] of integer;
e:array[1..5,1..10] of integer;

数组定义后就不能修改大小了,这个很多语言(C语言等)都是这样的,如果想要使用运行时大小的数据则:

type darray = array of integer;
var a:darray;
b:array of array of integer;
begin
setlength(a,100);
end;

集合

var s1: set of 'a' .. 'z';
  s2:set of 'a'..'z';
  s3: set of 'a'..'z';

s1 := ['a','b','c'];
s2 := ['c','e','d'] ;

s3 := s1 + s2; //union
s3 := s1 - s2; //difference
s3 := s1 * s2; // intersection

集合元素不重复,可以支持交,并,差等集合操作

文件和记录

type Student = record
  id:integer;
  name:string[20];  
end;
var FileA:file of integer;
  FileB:file of Student;
  FileC: textfile;
  s:Student;
begin
  assignfile(FileC,"file-c.txt");
  append(FileC);

  writeln(fileC,'Hello');
  closefile(FileC);

  assignfile(FileB,'file-b.dat');
  rewrite(FileB);
  s.id := 10;
  s.name := 'tom';

  write(f,s);
  closefile(f);

end;  

类

看到前面有记录record,class和record类似.record出现的早,class是后来加的.

record 特点:

• 不支持继承
• 不支持方法
• 支持栈,堆内存
• 支持变体
• 不支持作用域

class 特点:

• 支持继承
• 支持方法
• 支持堆内存
• 不支持变体类型
• 支持作用域

代码示例

//无具体要解决的问题,只是演示pascal语法

program demo02;

{$mode delphi}{$H+}
{$I+} // Errors will lead to an EInOutError exception (default)
uses SysUtils,Classes;

type Gender = (Male,Female);
type Weekday = (Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday);
type Workday = Monday..Friday;
type Weekend = Saturday..Sunday;  
type Person = record
  id:integer;
  name:string[20];
end;

type Student = record
  id :integer;
  name:string;
  fgender:Gender; 
  other:variant;

end;



type Teacher = class
private 
  FId :integer;
  FName:string; 
  LessionAt: array of Weekday; //上课时间
  procedure SetName(n:string);
public    
  property Id:integer read FId write FId;
  property Name:string read FName write SetName;
  procedure Hello();  
end;

procedure Teacher.SetName(n:string);
begin
  // data validation
  Self.FName := n;
end;

procedure Teacher.Hello();
begin
  writeln(FId,FName);
end;
procedure StudentHello(s:Student);
begin
  writeln(s.id,s.name);
end;  

var s:Student;  
  s2:^Student;
  t:Teacher;  
  p:Person;
  f1: file of integer;
  f2: file of Person;
  f3: TextFile;
  ss:string;
begin


  s.id := 10;
  s.name := 'tom';
  s.other := TRUE;
  s.other := 'test';
  StudentHello(s);


  s2 := getmem(sizeof(Student));
  s2.id := 20;
  s2.name := 'jerry';
  StudentHello(s2^);
  freemem(s2);

  new(s2);
  if not assigned(s2) then
  begin
    writeln('error ');
    exit();
  end
  else
  begin
    s2.id := 50;
    s2.name := 'Tomas';
    StudentHello(s2^);
    freemem(s2);
  end;


  t := Teacher.Create;
  try
    t.id := 30;
    t.name := 'davaid';
    setlength(t.LessionAt,3);
    
    t.LessionAt[0] := Wednesday;    
    t.LessionAt[1] := Thursday;   
    t.LessionAt[2] := Friday;   
    
    t.Hello();
  finally
    t.Free;
  end;


  AssignFile(f1,'f1.dat');
  try
    rewrite(f1);
    write(f1,10);
    write(f1,20);
    CloseFile(f1);
  except on E: EInOutError do
     writeln('File handling error occurred. Details: ', E.Message);
    end;

    AssignFile(f2,'f2.dat');
    rewrite(f2);
    p.id := 120;
    p.name := 'mike';
    write(f2,p);
    CloseFile(f2);

    p.name := 'tom';

    AssignFile(f2,'f2.dat');
    reset(f2);
    read(f2,p);
    assert(p.name = 'mike');
    CloseFile(f2);




    AssignFile(f3,'f3.txt');
    if FileExists('f3.txt') then
    append(f3)
  else
    rewrite(f3);
    writeln(f3,'hello world');
    writeln(f3,'bye');
    CloseFile(f3);


    AssignFile(f3,'d02.pas');
    reset(f3);
    while not eof(f3) do
    begin
      readln(f3, ss);
      writeln(ss);
    end;
    CloseFile(f3);
end.