Str(-1.4:2:1, T);
S := S + T + '''' rounds to '''' + IntToStr(Round(-1.4)) + #13#10;
Str(-1.5:2:1, T);
S := S + T + '''' rounds to '''' + IntToStr(Round(-1.5));
MessageDlg(S, mtInformation, [mbOk], 0);
end;
-----------------------------------------------------------------------------
Trunc 将实数转为整数.(小数直接舍弃)
-----------------------------------------------------------------------------
Unit System
函数原型 function Trunc(X: Extended): Longint;
Untyped file routines
var
S, T: string;
begin
Str(1.4:2:1, T);
S := T + '''' Truncs to '''' + IntToStr(Trunc(1.4)) + #13#10;
Str(1.5:2:1, T);
S := S + T + '''' Truncs to '''' + IntToStr(Trunc(1.5)) + #13#10;
Str(-1.4:2:1, T);
S := S + T + '''' Truncs to '''' + IntToStr(Trunc(-1.4)) + #13#10;
Str(-1.5:2:1, T);
S := S + T + '''' Truncs to '''' + IntToStr(Trunc(-1.5));
MessageDlg(S, mtInformation, [mbOk], 0);
end;
-------------------------
var
f: file of Integer;
i,j: Integer;
begin
AssignFile(f,''''TEST.INT'''');
Rewrite(f);
for i := 1 to 6 do
Write(f,i);
Writeln(''''File before truncation:'''');
Reset(f);
while not Eof(f) do
begin
Read(f,i);
Writeln(i);
end;
Reset(f);
for i := 1 to 3 do
Read(f,j); { Read ahead 3 records }
Truncate(f); { Cut file off here }
Writeln;
Writeln(''''File after truncation:'''');
Reset(f);
while not Eof(f) do
begin
Read(f,i);
Writeln(i);
end;
CloseFile(f);
Erase(f);
end;
-----------------------------------------------------------------------------
BlockRead 读取档案至记忆体区块.
-----------------------------------------------------------------------------
procedure TForm1.Button1Click(Sender: TObject);
var
FromF, ToF: file;
NumRead, NumWritten: Integer;
Buf: array[1..2048] of Char;
begin
if OpenDialog1.Execute then { 开档对话盒}
begin
AssignFile(FromF, OpenDialog1.FileName);{}
Reset(FromF, 1); { Record size = 1 }
if SaveDialog1.Execute then { Display Save dialog box}
begin
AssignFile(ToF, SaveDialog1.FileName);{ Open output file }
Rewrite(ToF, 1); { Record size = 1 }
Canvas.TextOut(10, 10, ''''Copying '''' + IntToStr(FileSize(FromF))+''''bytes...'''');
repeat
BlockRead(FromF, Buf, SizeOf(Buf), NumRead);
BlockWrite(ToF, Buf, NumRead, NumWritten);
until (NumRead = 0) or (NumWritten <> NumRead);
CloseFile(FromF);
CloseFile(ToF);
end;
end;
end;
## BlockRead, BlockWrite, SaveDialog Example
-----------------------------------------------------------------------------
BlockWrite 将记忆体区块写入档案.
-----------------------------------------------------------------------------
Unit System
函数原型 procedure BlockRead(var F: File; var Buf; Count: Integer
[; var Result: Integer]);
函数原型 procedure BlockWrite(var f: File; var Buf; Count: Integer
[; var Result: Integer]);
范例 var
FromF, ToF: file;
NumRead, NumWritten: Integer;
Buf: array[1..2048] of Char;
begin
if OpenDialog1.Execute then
{ Display Open dialog box }
begin
AssignFile(FromF, OpenDialog1.FileName);
Reset(FromF, 1); { Record size = 1 }
if SaveDialog1.Execute then
{ Display Save dialog box }
begin
AssignFile(ToF, SaveDialog1.FileName);
{ Open output file }
Rewrite(ToF, 1); { Record size = 1 }
Canvas.TextOut(10, 10,''''Copying ''''+
IntToStr(FileSize(FromF))+ '''' bytes...'''');
repeat
BlockRead(FromF, Buf, SizeOf(Buf), NumRead);
BlockWrite(ToF, Buf, NumRead, NumWritten);
until (NumRead = 0) or (NumWritten <>
NumRead);
CloseFile(FromF);
CloseFile(ToF);
end;
end;
end;
======================================
Variant support routines 鬼牌变数函式
======================================
VarArrayCreate 建立一个variant array.
-----------------------------------------------------------------------------
Unit System
函数原型 function VarArrayCreate(const Bounds: array of Integer;
VarType: Integer): Variant;
范例 procedure TForm1.Button1Click(Sender: TObject);
var
A:Variant;
S:String;
begin
A:=VarArrayCreate([0,4],varVariant);
A[0]:=1;
A[1]:=1234.5678;
A[2]:=''''Hello world'''';
A[3]:=TRUE;
A[4]:=VarArrayOf([1 ,10 ,100 ,10000]);
S:=A[4][2];
S:=A[2]+'''' ''''+S;
Label1.Caption:=S;
end;
说明 S:=A[4][2]; Variant可以不用函数来做转换.
只能单独使用,如为下列则有误.
S:=A[2]+'''' ''''+A[4][2];
VarType
varEmpty $0000 The variant is Unassigned.
varNull $0001 The variant is Null.
varSmallint $0002 16-bit signed integer (type Smallint).
varInteger $0003 32-bit signed integer (type Integer).
varSingle $0004 Single-precision floating-point value
(type Single).
varDouble $0005 Double-precision floating-point value
(type Double).
varCurrency $0006 Currency floating-point value (type Currency).
VarDate $0007 Date and time value (type TDateTime).
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