frustrated bout char array

This is a discussion on frustrated bout char array within the C++ Programming forums, part of the General Programming Boards category; hello! is there a way to declare a char array of length that will be determined by a variable later? ...

  1. #1
    Registered User
    Join Date
    Jun 2005
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    8

    frustrated bout char array

    hello! is there a way to declare a char array of length that will be determined by a variable later?

    i'm working on a syntax checker program for a programming language and i have to use strlen() to check the longest line of code in the program before i can declare the length of the char array.

    i know that i can use string or other containers for this but the library my professor gave me accepts only char array. for now, i'm just declaring a char array of size 901 but i know this would not be acceptable.

  2. #2
    Registered User major_small's Avatar
    Join Date
    May 2003
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    try this:
    Code:
    #include<iostream>
    #include<cctype>
    
    int main()
    {
            char*line;
            int num;
    
            std::cout<<"Enter the size: ";
            std::cin>>num;
    
            line=new char[num];
    
            for(int i=0;i<num;i++)
            {
                    line[i]='1';
            }
    
            std::cout<<"A char array of "<<strlen(line)<<" elements has been created\n";
            delete[]line;
            return 0;
    }
    not a great example, but I think it gets the point across...
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  3. #3
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    >i'm just declaring a char array of size 901 but i know this would not be acceptable

    That probably isn't as oddball as you might think. For example, you might do something like this:

    1)assign 901 to a const int representing a number likely to be longer than the likely maximum length. Declare a char array using the const int to temporarilyuhold each
    line as you evaluate it it's actual length.

    2)use a loop to read the file/program one line at a time using getline, the char array
    from #1 above, and the const int.

    3)within the loop determine the actual length of each line. compare it to a variable representing the longest line in the program found so far. if length of current line is
    longer than length of longest line found so far, assign current length to variable holding
    value of longest line found so far.

    4)at end of loop use the actual maximum length found + 1 to declare the size of the
    length of the char array you will use the rest of the program.
    You're only born perfect.

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