help-function.txt

DELPHI常用函数集及简要范例集

 _HELP函数集
●●●●●●●
------------------------------------------------------------------
abs(x)    绝对值
arctan(x) 反正切
cos(x)    传回馀弦函数值
exp(x)    e的x次幂
frac(x)   取小数部分
int(x)    取整
ln(x)     自然对数
sin(x)    传回正弦函数值 
sqr(x)    x*x
sqrt(x)   平方根
其它
pred(x)   pred('D')='C', pred(true)=1;
succ(x)   succ('Y')='Z', succ(pred(x))=x
ord(x)    求x在字符集中的序号,如ord('A')=65
chr(x)    chr(65)='A'
round(x)  四舍五入
trunc(x)  trunc(4.8)=4,trunc('-3.6')=-3
upcase(x) upcase('a')='A'
hi(I)     hi($2A30)=$2A
lo(I)     lo($2A30)=$30
random(n) 产生[0,n)间的随机整数
sizeof(name)  求出某类型或变量在内存中占用的字节数
swap(num)     swap($3621)=$2136
================================
Arithmetic routines		数学运算
================================
Abs				绝对值
---------------------------------------------------------
Unit		System
函数原型	function Abs(X);
说明		X为整数or实数.
范例	
var
  r: Real;
  i: Integer;
begin
  r := Abs(-2.3);		{ 2.3 }
  i := Abs(-157);		{ 157 }
end;
----------------------------------------------------------
ArcTan			三角函数
----------------------------------------------------------
范例
Cos
var R: Extended;
begin
  R := Cos(Pi);
end;
----------------------------------------------------------
Sin
----------------------------------------------------------
范例
var
  R: Extended;
  S: string;
begin
  R := Sin(Pi);
  Str(R:5:3, S);
  Canvas.TextOut(10, 10, 'The Sin of Pi is ' + S);
end;
----------------------------------------------------------
Unit		System
函数原型	function ArcTan(X: Extended): Extended;
函数原型	function Cos(X: Extended): Extended;
函数原型	function Sin(X: Extended): Extended;
----------------------------------------------------------
说明		X为径度.
			Tan(x) === Sin(x) / Cos(x)
			ArcSin(x) = ArcTan (x/sqrt (1-sqr (x)))
			ArcCos(x) = ArcTan (sqrt (1-sqr (x)) /x)
			左边这三个不是函数,而是右边运算求得.
范例
var
  R: Extended;
begin
  R := ArcTan(Pi);
end;
范例		var
			  R: Extended;
			  S: string;
			begin
			  R := Sin(Pi);
			  Str(R:5:3, S);
			  Canvas.TextOut(10, 10, 'The Sin of Pi is ' + S);
			end;
----------------------------------------------------------
Frac				求一个实数的小数部份
----------------------------------------------------------
Unit		System
函数原型	function Frac(X: Real): Real;
说明		X为实数.
范例		var
			  R: Real;
			begin
			  R := Frac(123.456);		{ 0.456 }
			  R := Frac(-123.456);		{ -0.456 }
			end;
------------------------------------------
Int					求一个实数的整数部份
------------------------------------------
Unit		System
函数原型	function Int(X: Real): Real;
说明		X为实数.
范例		var 
			  R: Real;
			begin
			  R := Int(123.456);		{ 123.0 }
			  R := Int(-123.456);		{ -123.0 }
			end;
------------------------------------------
Pi					就是数学的Pi
------------------------------------------
Unit		System
函数原型	function Pi: Extended;
说明		它是一个函数,但我们就把它当作是预设的变数来用吧!
			Pi= 3.1415926535897932385
------------------------------------------
Sqr					X的平方
-----------------------------------------
范例
var
  S, Temp: string;
begin
   Str(Sqr(5.0):3:1, Temp);
   S := '5 squared is ' + Temp + #13#10;
   Str(Sqrt(2.0):5:4, Temp);
   S := S + 'The square root of 2 is ' + Temp;
   MessageDlg(S, mtInformation, [mbOk], 0);
end;
-----------------------------------------
Sqrt				X的平方根
------------------------------------------
Unit		System
函数原型	function Sqr(X: Extended): Extended;
函数原型	function Sqrt(X: Extended): Extended;
范例		var
			  S, Temp: string;
			begin
			  Str(Sqr(5.0):3:1, Temp);
			  S := '5 squared is ' + Temp + #13#10;
			  Str(Sqrt(2.0):5:4, Temp);
			  S := S + 'The square root of 2 is ' + Temp;
			  MessageDlg(S, mtInformation, [mbOk], 0);
			end;
------------------------------------------
Ln					自然对数
------------------------------------------
范例
var
   e : real;
   S : string;
begin
   e := Exp(1.0);
   Str(ln(e):3:2, S);
   S := 'e = ' + FloatToStr(e) + '; ln(e) = ' + S;
   Canvas.TextOut(10, 10, S);
end;
----------------------------------------
Exp				指数
------------------------------------------
Unit		System
函数原型	function Ln(X: Real): Real;
函数原型	function Exp(X: Real): Real;
范例		var
			  e : real;
			  S : string;
			begin
			  e := Exp(1.0);
			  Str(ln(e):3:2, S);
			  S := 'ln(e) = ' + S;
			  Canvas.TextOut(10, 10, S);
			end;
------------------------------------------
 Date and time routines	日期及时间函数
------------------------------------------
Date				传回目前的日期
Unit		SysUtils
函数原型	function Date: TDateTime;
范例		procedure TForm1.Button1Click(Sender: TObject);
			begin
			  Label1.Caption := 'Today is  ' + DateToStr(Date);
			end;
------------------------------------------
DateTimeToStr	日期时间转换成内定型字串(1996/12/20 09:12:20 PM)
------------------------------------------
Unit		SysUtils
函数原型	function DateTimeToStr(DateTime: TDateTime): string;
范例		procedure TForm1.Button1Click(Sender: TObject);
			begin
			  Label1.Caption := DateTimeToStr(Now);
			end;
--------------------------------------------------------
DateTimeToString	日期时间转换成自定型字串
-------------------------------------------------------
Unit		SysUtils
函数原型	procedure DateTimeToString(var Result: string; const Format: 
				string; DateTime: TDateTime);
范例		procedure TForm1.FormCreate(Sender: TObject);
			var
			  s:string;
			begin
			  DateTimeToString(s,'dddd,mmmm d,yyyy  "at" hh:mm 
				AM/PM',Now);
			  Label1.Caption :=s;
			end;
结果		星期五,十二月 20,1996 at 09:20 PM
-----------------------------------------------------------------------------
**** 	Format格式叁考下面.FormatDateTime.
--------------------------------------------------------
DateToStr			日期转换成内定型字串.(1996/12/20)
--------------------------------------------------------
Unit		SysUtils
函数原型		function DateToStr(Date: TDateTime): string;
范例
procedure TForm1.Button1Click(Sender: TObject);
begin
  Label1.Caption := 'Today is  ' + DateToStr(Date);
end;
# Date, DateToStr Example
--------------------------------------------------------
DayOfWeek		求叁数日期是星期几.
--------------------------------------------------------
Unit		SysUtils
函数原型	function DayOfWeek(Date: TDateTime): Integer;
说明		传回值是一整数,1~7.
			星期日为1.
范例
procedure TForm1.Button1Click(Sender: TObject);
var
  ADate: TDateTime;
  days: array[1..7] of string;
begin
  days[1] := 'Sunday';
  days[2] := 'Monday';
  days[3] := 'Tuesday';
  days[4] := 'Wednesday';
  days[5] := 'Thursday';
  days[6] := 'Friday';
  days[7] := 'Saturday';
  ADate := StrToDate(Edit1.Text);
  ShowMessage(Edit1.Text + ' is a ' + days[DayOfWeek(ADate)];
end;
# StrToDate, DayOfWeek Example
--------------------------------------------------------
DecodeDate		将TDateTime型态的日期变数，转为Word型态.
--------------------------------------------------------
范例
procedure TForm1.Button1Click(Sender: TObject);
var
  Present: TDateTime;
  Year, Month, Day, Hour, Min, Sec, MSec: Word;
 begin
  Present:= Now;
  DecodeDate(Present, Year, Month, Day);
  Label1.Caption := 'Today is Day ' + IntToStr(Day) + ' of Month '
    + IntToStr(Month) + ' of Year ' + IntToStr(Year);
  DecodeTime(Present, Hour, Min, Sec, MSec);
  Label2.Caption := 'The time is Minute ' + IntToStr(Min) + ' of Hour '
    + IntToStr(Hour);
end;
# DecodeDate, DecodeTime Example
--------------------------------------------------------
DecodeTime		将TDateTime型态的时间变数，转为Word型态.
--------------------------------------------------------
Unit		SysUtils
函数原型	procedure DecodeDate(Date: TDateTime; var Year, Month,Day: Word);
函数原型	procedure DecodeTime(Time: TDateTime; var Hour, Min, Sec,MSec: Word);
范例 	procedure TForm1.Button1Click(Sender: TObject);
			var
			  Present: TDateTime;
			  Year, Month, Day, Hour, Min, Sec, MSec: Word;
			begin
			  Present:= Now;
			  DecodeDate(Present, Year, Month, Day);
			  Label1.Caption := 'Today is Day ' + IntToStr(Day) + ' of 
				Month ' +	IntToStr(Month) + ' of Year ' + IntToStr(Year);
			  DecodeTime(Present, Hour, Min, Sec, MSec);
			  Label2.Caption := 'The time is Minute ' +IntToStr(Min) + ' of 
				Hour ' + IntToStr(Hour);
			end;
--------------------------------------------------------
EncodeDate		将Word型态的日期变数，转为TDateTime型态.
--------------------------------------------------------
范例
procedure TForm1.Button1Click(Sender: TObject);
var
  MyDate: TDateTime;
begin
  MyDate := EncodeDate(StrToInt(Edit1.Text), StrToInt(Edit2.Text), StrToInt(Edit3.Text));
  Label1.Caption := DateToStr(MyDate);
end;
-------------------------------------------------------
EncodeTime		将Word型态的时间变数，转为TDateTime型态.
--------------------------------------------------------
Unit		SysUtils
函数原型	function EncodeDate(Year, Month, Day: Word): TDateTime;
函数原型	function EncodeTime(Hour, Min, Sec, MSec: Word): 
				TDateTime;
范例		procedure TForm1.Button1Click(Sender: TObject);
			var
			  MyDate: TDateTime;
			  MyTime: TDateTime;
			begin
			  MyDate := EncodeDate(83, 12, 31);
			  Label1.Caption := DateToStr(MyDate);
			  MyTime := EncodeTime(0, 45, 45, 7);
			  Label2.Caption := TimeToStr(MyTime);
			end;
范例
procedure TForm1.Button1Click(Sender: TObject);
var
  MyTime: TDateTime;
begin
  MyTime := EncodeTime(0, 45, 45, 7);
  Label1.Caption := TimeToStr(MyTime);
end;
--------------------------------------------------------
FormatDateTime	将日期时间依Format的格式转换给一字串.
--------------------------------------------------------
Unit		SysUtils
函数原型	function FormatDateTime(const Format: string; DateTime: 
				TDateTime): string;
****		类似DateTimeToString.
Format格式
c		内定值ShortDateFormat的格式.(1996/12/20 09:20:15 PM).
d		日期,前面不补0.(1-31)
dd		日期,前面补0.(01-31)
ddd		星期.(星期日).
Dddd		中文2.01版,同上.
ddddd	日期.(1996/12/20)
dddddd	日期.(1996年12月20日)
m		月份,前面不补0.(1-12)
mm		月份,前面补0.(01-12)
mmm	中文显示.(十二月)
mmmm	中文2.01版,同上.
Yy		年度.(00-99)
yyyy		年度.(0000-9999)
h		小时.(0-23)
hh		小时.(00-23)
n		分钟.(0-59)
nn		分钟.(00-59)
s		秒钟.(0-59)
ss		秒钟.(00-59)
t		时间.(09:20 PM)
tt		时间.(09:20:15 PM)
am/pm	单独显示am or pm.(若大写,则显示大写)
a/p		单独显示a or p.
范例
The following example assigns 'The meeting is on Wednesday, February 15, 1995 at 10:30 AM' to the string variable S. 
S := FormatDateTime('"The meeting is on " dddd, mmmm d, yyyy, " at " hh:mm AM/PM',
   StrToDateTime('2/15/95 10:30am'));//???
--------------------------------------------------------
Now				传回目前的日期时间.
--------------------------------------------------------
Unit		SysUtils
函数原型	function Now: TDateTime;
范例
procedure TForm1.Button1Click(Sender: TObject);
begin
  Label1.Caption := DateTimeToStr(Now);
end;
# Now, DateTimeToStr Example
--------------------------------------------------------
StrToDate			将字串转为TDateTime型态的日期.
--------------------------------------------------------
Unit		SysUtils
函数原型	function StrToDate(const S: string): TDateTime;
范例		procedure TForm1.Button1Click(Sender: TObject);
			var
			  ADate: TDateTime;
			begin
			  ADate := StrToDate(Edit1.Text);
			  Label1.Caption := DateToStr(ADate);
			end;
范例
procedure TForm1.Button1Click(Sender: TObject);
var
  ADate: TDateTime;
  days: array[1..7] of string;
begin
  days[1] := 'Sunday';
  days[2] := 'Monday';
  days[3] := 'Tuesday';
  days[4] := 'Wednesday';
  days[5] := 'Thursday';
  days[6] := 'Friday';
  days[7] := 'Saturday';
  ADate := StrToDate(Edit1.Text);
  ShowMessage(Edit1.Text + ' is a ' + days[DayOfWeek(ADate)];
end;
# StrToDate, DayOfWeek Example
--------------------------------------------------------
StrToDateTime	将字串转为TDateTime型态的日期时间.
--------------------------------------------------------
Unit		SysUtils
函数原型	function StrToDateTime(const S: string): TDateTime;
范例
procedure TForm1.Button1Click(Sender: TObject);
var
  ADateAndTime: TDateTime;
begin
  ADateAndTime := StrToDateTime(Edit1.Text);
  Table1.FieldByName('TimeStamp').AsDateTime := ADateAndTime;
end;
--------------------------------------------------------
StrToTime			将字串转为TDateTime型态的时间.
--------------------------------------------------------
Unit		SysUtils
函数原型	function StrToTime(const S: string): TDateTime;
范例
procedure TForm1.Button1Click(Sender: TObject);
var
  ATime: TDateTime;
begin
  ATime := StrToTime(Edit1.Text);
  if ATime < 0.50 then