DELPHI常用函数集及简要范例-数学运算

_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