我有一个具有特定结构的文本文件,即(对于每一行):字符、空格、字符、空格、双精度浮点数值、换行符。例如:
q w 1.23
e r 4.56
t y 7.89
什么是在Free Pascal中“提取”这些值的正确方法?
我有一个具有特定结构的文本文件,即(对于每一行):字符、空格、字符、空格、双精度浮点数值、换行符。例如:
q w 1.23
e r 4.56
t y 7.89
FreePascal中的SysUtils有一个名为SScanF的函数(你可能在其他语言中知道它..)
我修改了RRUZ的示例以展示如何使用它。
uses SysUtils;
type
TData=object
Val1 ,
Val2 : String;
Val3 : Double;
end;
procedure ProcessFile(aFileName:String);
var
F : Text;
LData : TData;
Line : String;
begin
DecimalSeparator:='.';
AssignFile(F,aFileName);
Reset(F);
while not eof(F) do
begin
ReadLn(F,Line);
SScanf(Line,'%s %s %f',[@LData.Val1,@LData.Val2,@LData.Val3]);
//do something with the data
WriteLn(LData.Val1);
WriteLn(LData.Val2);
WriteLn(LData.Val3);
end;
end;
begin
ProcessFile('C:\Bar\Foo\Data.txt');
Writeln('Press Enter to exit');
Readln;
end.
TStringList
类来加载文件,并使用 DelimitedText
属性将值拆分到另一个 TStringList 中,然后将这些值存储在记录中。{$mode objfpc}{$H+}
uses
Classes, SysUtils;
{$R *.res}
type
TData=record
Val1: Char;
Val2: Char;
Val3: Double;
end;
procedure ProcessFile;
var
LFile : TStringList;
Line : TStringList;
i : Integer;
LData : TData;
LFormat: TFormatSettings;
begin
//set the propert format for the foat values
LFormat:=DefaultFormatSettings;
LFormat.DecimalSeparator:='.';
LFile:=TStringList.Create;
Line :=TStringList.Create;
try
//load the file
LFile.LoadFromFile('C:\Bar\Foo\Data.txt');
Line.Delimiter:=' ';
for i:=0 to LFile.Count-1 do
begin
//read the line and split the result
Line.DelimitedText:=LFile[i];
//some basic check
if Line.Count <> 3 then raise Exception.Create('Wrong data length');
//you can add additional check here
LData.Val1:=Line[0][3];
LData.Val2:=Line[1][4];
LData.Val3:=StrToFloat(Line[2],LFormat);
//do something with the data
WriteLn(LData.Val1);
WriteLn(LData.Val2);
WriteLn(LData.Val3);
end;
finally
Line.Free;
LFile.Free;
end;
end;
begin
try
ProcessFile;
except on E:Exception do Writeln(E.Classname, ':', E.Message);
end;
Writeln('Press Enter to exit');
Readln;
end.
program WeightFileRead;
uses SysUtils, StrUtils;
var
MyFile : TextFile;
FirstChar, SecondChar, DummyChar : Char;
Weight : Double;
begin
if GetCmdLineArg ('editweights', StdSwitchChars) = ''
then begin
WriteLn ('Syntax: WeightFileRead -editweights filename'); exit
end;
AssignFile (MyFile, GetCmdLineArg ('editweights', StdSwitchChars));
Reset (MyFile);
try
while not EOF (MyFile) do
begin
ReadLn (MyFile, FirstChar, DummyChar, SecondChar, Weight);
WriteLn ('A: ', FirstChar, '; B: ', SecondChar, '; W: ', Weight:0:1);
end
finally
CloseFile (MyFile)
end
end.
ExtractWord
来查找字符串中第n
个以空格分隔的单词(或者使用ExtractSubstr
将多个空格视为引入一个空单词),并将第三个转换为数字。program WeightFileRead2;
uses SysUtils, StrUtils;
var
MyFile : TextFile;
FileLine : String;
begin
if GetCmdLineArg ('editweights', StdSwitchChars) = ''
then begin
WriteLn ('Syntax: WeightFileRead -editweights filename'); exit
end;
AssignFile (MyFile, GetCmdLineArg ('editweights', StdSwitchChars));
Reset (MyFile);
try
while not EOF (MyFile) do
begin
ReadLn (MyFile, FileLine);
WriteLn ('A: ', ExtractWord (1, FileLine, [' ']),
'; B: ', ExtractWord (2, FileLine, [' ']),
'; W: ', StrToFloat (ExtractWord (3, FileLine, [' '])):0:1);
end
finally
CloseFile (MyFile)
end
end.
[' ']
而不是StdWordDelims
,因为我不希望.或,成为单词分隔符。