Re: C++ programming: keeping count of data items read from file
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Mark Allums wrote:
> H.S. wrote:
>> Hello,
>>
>> In a C++ program I am reading a data file for later processing and
>> computations. While reading that data file, I want to keep track of
>> data items (doubles) read.
>>
>> The data file is just a text file with N lines with C doubles in each
>> line (N and C are known a priori). For now, I just read from the file
>> stream in to a 2D array variable by reading each double at a time.
>>
>> Now I am trying to introduce some sanity checking into this reading
>> block. Here is what I am trying to do:
>> 1. Verify how many doubles I have read in each line. Must be C. If
>> they are not C, then the input file is corrupt.
>> 2. Verify that the total number of data items are NxC. This is simple,
>> I just keep a track of how many numbers I have read.
>>
>> So, how do I go about doing (1) above? I was thinking of somehow
>> checking if I have reached the end of line somehow (EOL?) but haven't
>> found a method to do so. All I have found is EOF.
>>
>> thanks,
>> ->HS
>>
>>
>
> Not directly helpful, but some suggestions:
>
> 1. You might want to learn PERL or Python or Ruby, and do it there.
FWIW, this is very easy to do in Python.
PSFWIW: Satan uses Ruby.
> 2. If it has to be C++, learn enough PERL to write a filter for the data
> file, and transform it so that it has one double per line.
> 3. Debug the data generator /in situ/ with a good debugger, and bypass
> the need to do the sanity checking.
> 4. Find a good C++ reference, and use it. There are several.
>
> Slightly more helpful:
>
> 1. Read one line at a time in as a string, then operate on the string.
> 2. C++ has the ability to do everything that C does in a low level way,
> but why? Use the C++ way, or use the C way:
>
> #include <cstdio>
> #include <iostream>
> . . .
> using namespace std;
> . . .
> ios::sync_with stdio();
> . . .
> int blah = fscanf(somefile,"%f %f %f %f\n", d1,d2,d3,d4);
> if (blah != correctvalue)
> {
> dosomething();
> closefiles();
> cout << "error in data file\n";
> exit(1);
> }
> . . .
> // etc.
>
>
> (The ios::sync_with_stdio(); line may differ slightly on different C++
> implementations. I haven't used it in a while. May be spelled synch_.
> Too lazy to look it up.
>
> The fscanf line may just be wrong. I quit writing C programs years ago.
> Too old, memory failing.)
>
>
>
Rich
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