String/Char* Problem in GMP

This is a discussion on String/Char* Problem in GMP within the C++ Programming forums, part of the General Programming Boards category; I am using the GMP multiple precison package. I need to input very large integers as strings, for example Code: ...

  1. #1
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    String/Char* Problem in GMP

    I am using the GMP multiple precison package.

    I need to input very large integers as strings, for example
    Code:
    mpz_init_set_str(x,"1234567890",10)
    will set x to that large integer in quotes (10 gives the base.)

    I want to be able to have the user enter the value, so I did something like:
    Code:
    #include <string>
    #include <gmpxx.h> // GMP
    
    string num;
    std::cin >> num;
    mpz_init_set_str(x,num,10)
    but this causes g++ to give the following error:
    error: cannot convert `std::string' to `const char*' for argument `2' to `int __gmpz_init_set_str(__mpz_struct*, const char*, int)'

    Any ideas how to input a data type that will work?

    I am using Ubuntu on an AMD64.

    Thanks!

  2. #2
    C++ Witch laserlight's Avatar
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    You need to use the c_str() member function, e.g. num.c_str()
    C + C++ Compiler: MinGW port of GCC
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  3. #3
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    nevermind i seriously need to start paying attention
    when i know im half asleep
    Last edited by ILoveVectors; 08-27-2005 at 01:27 AM.

  4. #4
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    Quickest problem solution ever.

    Thanks!

  5. #5
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    plz elaborate

    Laser light

    Could you please elaborate on the use of c_srt() function?

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