type checking?

Dear All!

I am trying to read lines from an input file. in one line There a are some words and double type numbers. I would like to assign these values to some string variables and double variables. For that reason I have to know the type of variable.
What is the best way? Any help appreciated. thanks!

code part ia mtrying to read the input file is the following: you can complete it.

Code:

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 string line, temp;
 double number;
 while(getline(fmonju,line)){
  if(!line.empty()){
    istringstream iss(line);
    while(iss.good()){
        iss>>temp; // ????
        iss>>number; // ???
    }
  }                         
 }

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Are you saying that the data in your input file MAY be a string, OR a double? You probably will be best off scanning the line for digits, then attempt to read the number from the first digit you find...

--
Mats

Yes, input file inlcude many lines of data. in one line there are 5 or 6 columns (it may change). these columns may be string or a double like that:

1 3 ABB DD 5
2 4 GT ty 4
. . . .. .
. . . . .
. . . . .

Then you need to read the entire line, then "split" it into portions "by hand", by checking the starting letter of each "chunk" of input, and decide if it's a number or text.

--
Mats

You'll need to write your own class. The class will have a string and a double in it and will know what type of cell it is.

Another question is what you are going to do with temp and number (you are not trying to read some randomly organized file for no good reason?).

Anyhow, you might just try to convert every word to a double and if that fails, you have a string. boost has lexical_cast, but you could also write a function that attempts the conversion using stringstream.

King Mir : I did not understand what type of class you mean. I will be pleased if you could give a simple example.

Quote:

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Another question is what you are going to do with temp and number (you are not trying to read some randomly organized file for no good reason?).

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I will do some simple change in the number, I will write into another file.

Quote:

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Anyhow, you might just try to convert every word to a double and if that fails, you have a string. boost has lexical_cast, but you could also write a function that attempts the conversion using stringstream.

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I am not good at using string streams, could you give a simple example. Thank you.

string streams used for conversion

Here's one way to look at it: every possible number can be represented as a string, but not vice versa. So you could read in each number/string as a string, look at it for digits, and if there are any, convert the string to a number.

Quote:

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Originally Posted by wolfindark

King Mir : I did not understand what type of class you mean. I will be pleased if you could give a simple example.

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It would look something like this:

Code:

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class StringOrDouble{
    private:
        std::string stringVersion;
        double doubleVersion;
        boolean typeIsDouble;
    public:
        boolean isDouble(){
            return typeIsDouble;
        }
        std::string getString(){
              if(typeIsDouble)
                  throw myException();
              return stringVersion;
      }
      void set(std::string){
            //code for determining if value is a double goes here.
            //should also set stringVersion or doubleVersion.
      }
};

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You're confusing camel notation with "underscore notation". (string_version, stringVersion, . . . .)

You don't need to write your own class, it would just be a good idea.

Quote:

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Originally Posted by dwks

You're confusing camel notation with "underscore notation". (string_version, stringVersion, . . . .)

You don't need to write your own class, it would just be a good idea.

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Fixed the notation.

Chances are, a class is the way to go. A class is the best way to store a value that can be one of two types. This is C++ after all, not C.