DELPHI常用函数集及简要范例

_HELP 函数集

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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

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

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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 }

Cos

var R: Extended;

begin

R := Cos(Pi);

end;

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Sin

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R: Extended;

S: string;

begin

R := Sin(Pi);

Str(R:5:3, S);

Canvas.TextOut(10, 10, 'The Sin of Pi is ' + S);

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Unit System

函数原型 function Sin(X: Extended): Extended;

范例

var

R: Extended;

begin

R := ArcTan(Pi);

end;

范例 var

R: Extended;

S: string;

begin

end;

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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 }

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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;

函数原型 function Pi: Extended;

Pi= 3.1415926535897932385

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Sqr X 的平方

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范例

var

S, Temp: string;

begin

Str(Sqr(5.0):3:1, Temp);

S := '5 squared is ' + Temp + #13#10;

end;

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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;

S := S + 'The square root of 2 is ' + Temp;

MessageDlg(S, mtInformation, [mbOk], 0);

end;

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Ln 自然对数

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范例

var

e : real;

S : string;

begin

e := Exp(1.0);

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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);

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Date and time routines 日期及时间函数

Unit SysUtils

函数原型 function Date: TDateTime;

范例 procedure TForm1.Button1Click(Sender: TObject);

begin

Label1.Caption := 'Today is ' + DateToStr(Date);

end;

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Unit SysUtils

begin

Label1.Caption := DateTimeToStr(Now);

end;

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Unit SysUtils

string; DateTime: TDateTime);

Label1.Caption :=s;

end;

结果 星期五,十二月 20,1996 at 09:20 PM

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**** Format 格式叁考下面.FormatDateTime.

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DateToStr 日期转换成内定型字串.(1996/12/20)

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Unit SysUtils

范例

Label1.Caption := 'Today is ' + DateToStr(Date);