pulling 2 doubles from a string?

This is a discussion on pulling 2 doubles from a string? within the C++ Programming forums, part of the General Programming Boards category; I have been playing around with sscanf but I have recently read that it does not even support floats and ...

  1. #1
    Registered User
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    pulling 2 doubles from a string?

    I have been playing around with sscanf but I have recently read that it does not even support floats and doubles. true?

    Code:
    double c1,c2;
    
    string input = "guaranteed repair & support at (3.124, 391.111).";
    sscanf(input.c_str(),"%lf%lf%",&c1,&c2);
    doesnt save anything into c1, c2

    Code:
    double c1,c2;
    
    string input = "guaranteed repair & support at (3.124, 391.111).";
    sscanf(input.c_str(),"%*s%lf, %lf%).",&input, &c1,&c2);
    doesnt change anything


    anyone know a way to pull the doubles out of the string and save them in c1 and c2?
    (without explicitly iterating through the string and finding the (...) )

    THanks

  2. #2
    Master Apprentice phantomotap's Avatar
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    doesnt save anything into c1, c2
    Why would it? The `%lf' modifier (for `sscanf') reads a single `double'. There is no `double' at that point in the input.

    doesnt change anything
    Why would it? The `%s' modifier (for `sscanf') reads a single "word". There is more than one "word" before the first `double' value.

    I have been playing around with sscanf but I have recently read that it does not even support floats and doubles. true?
    You need to go read the standard documentation. What other sources may say is irrelevant.

    anyone know a way to pull the doubles out of the string and save them in c1 and c2?
    You need to go read the standard documentation. Programming isn't magic. You can't wave your bits around and hope for the best.

    Soma

    Code:
    #include <stdio.h>
    
    int main()
    {
    	double c1 = 0;
    	double c2 = 0;
    	char input[] = "guaranteed repair & support at (3.124, 391.111).\n";
    	if(2 == sscanf(input, "%*[^0123456789.]%lf%*[^0123456789.]%lf%*[^\n]%*[\n]", &c1, &c2))
    	{
    		printf("%f\n%f\n", c1, c2);
    	}
    	else
    	{
    		printf("error");
    	}
    	return(0);
    }

  3. #3
    CSharpener vart's Avatar
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    what about negative values?

    and what this thread has to do with C++ anyway? It should be moved to C-forum
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  4. #4
    Master Apprentice phantomotap's Avatar
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    what about negative values?
    What about different locals that don't use '.' as the radix separator?
    What about values expressed in other notations (scientific)?
    What about values expressed in a different base (16)?
    What if the type changes to `float' or `long double'?
    What if the string uses a MBCS?

    Do you want to post some source that can handle all of these potential changes for him? No? "You need to go read the standard documentation." ^_^

    and what this thread has to do with C++ anyway? It should be moved to C-forum
    Calm yourself. Unless you have the authority to move it, you'll have to wait.

    Soma

  5. #5
    Registered User UltraKing227's Avatar
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    it should be in the C-programming forum, and it can be done by asking the
    mods. but lets not bother them for now...

  6. #6
    Registered User UltraKing227's Avatar
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    by the way, rodrigorules, its not a good example of a C++ programmer
    using both C and C++ in a program. it can be used, but i dont think thats
    a good way of programming.

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