C / C++ / MFC

31-Jan-12 2:22

Once I have a long file with ascii text- long row of numbers. I used StrToD() to convert text to array of floating point numbers. I couldn't undrestand, why it works so slowly? Running it under debbugger, I realized what was the problem. This stupid function scanned the whole file, looking for null terminator! I think, there is no reason to scan long text string after set of chars, belonging to the first number has been obtained. Finally I had to write my own realisation of this function.

CPallini31-Jan-12 2:39

31-Jan-12 2:39

strtod (that is the 'standard' C++ strtod, I never heard about StrToD) is not 'strange': it is a function satisfying its own requirements that are clearly explained, for instance here[^]. If it doesn't fit your needs, then, well, the right way is to write your own one (as you did).

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

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[My articles]

a_matseevsky31-Jan-12 3:37

31-Jan-12 3:37

You are right about lowercase: strtod(const char *nptr, char **endptr) returns floating point value and a pointer to the first char, that stops scanning. It means, that if I have for example such string "12.3 0.07" and give pointer to this string to strtod for eating, it will return me 12.3 and pointer to the next char after '3'. Thats all right, no objections. But name me one reason to scan THE WHOLE string??? Why do not stop scanning after four first chars? It is my non-humble opinion: it typical left-hand approach.

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C^hris L^osinger31-Jan-12 4:04

C^hris L^osinger

31-Jan-12 4:04

strtod uses strlen, internally - at least in VS2008.

but VS2010 fixes this, reportedly.

a_matseevsky31-Jan-12 6:10

31-Jan-12 6:10

I use VS2005. I like it and this example of strange behavior is the only one what I actually met. No matter, build-in assembler lets me write compact and efficient procedures, when and if I have need in extra performance.

JackDingler31-Jan-12 11:54

JackDingler

31-Jan-12 11:54

Looks like you found a bug.

a_matseevsky31-Jan-12 12:32

C program to extract values from EXCEL file

31-Jan-12 12:32

I wouldn't say so: procedure works correctly. It is only inefficient realization, no more. I met a real bug in VS 6.0, but now it is of no use to speak about such ancient soft. Sometimes VS2005 asks me for confirmation, when I try to close prog, currently running under debugger, but it happens probably due to old age of my particulat exemplar.

Faez Shingeri31-Jan-12 1:46

Faez Shingeri

31-Jan-12 1:46

Hi,

Can we write a C program to get a particular column values from an EXCEL file and use them as input for another file.
Eg: I want to retrieve all the values of the 3rd column of an excel file and then use that value for searching in another text file and finally replacing it with "xyz".

Thanks,
Faez

CPallini31-Jan-12 2:35

31-Jan-12 2:35

Yes, we can.
You may have a look at one of the many articles about Excel automation[^] here at CodeProject.
They are mainly focused on C++ language however.
In fact the bad news of your task are that you have to call COM from C (feasible but bit involuted).

Faez Shingeri31-Jan-12 17:33

Faez Shingeri

31-Jan-12 17:33

I read the article regarding Excel automation and COM but could not find anything about extraction of values from a particular column of an Excel file.

I am using Eclipse IDE and gotta write a C code to open an Excel file and extract its fourth and fifth column values.

Any kinda help would be appreciated.

Thanks,
Faez

CPallini31-Jan-12 21:44

31-Jan-12 21:44

There are some examples on how to access cells, for instance via ADO: "How to Read and Write Excel Files in C++ via ADO"[^] or directly parsing the Excel file: "BasicExcel - A Class to Read and Write to Microsoft Excel"[^]

BTW I've balanced the pointless downvote.

Faez Shingeri31-Jan-12 22:51

Faez Shingeri

31-Jan-12 22:51

The below link helped me..

http://www.libxl.com

But now am facing other different problem

http://www.codeproject.com/Messages/4144507/Re-Undefined-reference-error-while-using-libxl-lib.aspx

Thanks for help

firmware coding in C

Ebe7230-Jan-12 23:16

Ebe72

30-Jan-12 23:16

Need help to understand this line of code
step = (struct MyStep*)BigStep
given,
typedef struct MyStep {...structure definition...};
const struct MyStep BigStep[]{...an array of MyStep...};

Thank you

Richard MacCutchan30-Jan-12 23:37

Richard MacCutchan

30-Jan-12 23:37

I don't know what version of C/C++ that is but it looks wrong to me. Why not show the exact code that you are trying to understand?

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CPallini31-Jan-12 2:25

31-Jan-12 2:25

That:

Takes BigStep (the address of the array of const MyStep structs).
Casts it to struct Mystep * (hence discarding the const constraint).
Assigns the result to step (that is probably defined as struct MyStep *).

Bram van Kampen31-Jan-12 12:27

Bram van Kampen

31-Jan-12 12:27

Hi,

Ebe72 wrote:
step = (struct MyStep*)BigStep
given,
typedef struct MyStep {...structure
definition...};
const struct MyStep BigStep[]{...an array of MyStep...};

Sorry, but by itself, this is Absolutely Meaningless. Firmware, Hardware, or Software Coding, makes no Real difference. It is something written in 'C'.
Question 1. Does your Code Compile.
If it does, you're lucky!
Question 2.
Does your code do what it is supposed to do.
If the answer is 'Yes' set a number of breakpoints around where the structure is used, and that will soon tell you (May take some patience) what happens, and what's what.

If your code does not Compile, you probably left out a Header. If it compiles, but does not link, you left out Library References.

If it Compiles and Links, but does not do what you expect, go back to the Docks and find out what it was supposed to do in the First Place!

Set Breakpoints, and find out what's going on.

This is a process called 'Debugging' It takes Time Skill and cunning, and the gray cells of 'Hercule Poirot'. It cannot be thaught as such, but you get experienced with your best friend, your Compiler.
Famous Chestnuts:-

<br />
if(x=0){...Do Something...} (Never Happens)<br />
<br />
int x==1;<br />
<br />
for(x=0;x=10;x++){...Do Something...}<br />
switch(){// In VC5 Trashes the Compiler<br />
break;<br />
}<br />

Hope this helps, if not, we need to see a little bit more than two lines of code, part of a Structure Definition. We are Not mindreaders Smile | :)

Bram van Kampen

::ifstream.open behaves differently in VC6 and VS2010

Erudite_Eric31-Jan-12 21:05

Erudite_Eric

31-Jan-12 21:05

BigStep[] is an array of MyStep structures. BigStep is a pointer to that array, iem the address of the first storage hole. ie, &BigStep[0].

'step as (MyStpe*)BigStep' points another pointer, this one a non const I assume (depending on how 'step' is declared), to the same address.

(BTW with the typedef you dont need to use ctruct MyStep* as the cast, MyStep* alone will compile since it is a new defined type.)

==============================

Nothing to say.

KASR130-Jan-12 22:31

KASR1

30-Jan-12 22:31

In VC6 when we use ::ifstream.open("test.txt") call creates a file if the specified file is not found in the location. But in VS2010 it does not create a file when its not found. Why is this differece and how to resolve this problem?

Re: ::ifstream.open behaves differently in VC6 and VS2010

CPallini30-Jan-12 22:42