Replacing characters

Hey,

I would like to replace every character in a string that is not a-z A-Z 0-9 or ' with a space. Currently I am trying to approach it this way:

Code:

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replace(ss.begin(), ss.end(), '!', ' ');

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Which would require dozens of those statements, one for each character that I don't want. Is there anyway to have the program check the string and convert any character that is not a-zA-Z' with a space, instead of writing individual replace statements?

Use transform. Write a function that takes a character and returns that character if it is alphanumeric, or ' ' if it is not.

So something like this?

Code:

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#include <ctype.h>

char checkVal(char x)
{
  if(isalnum(x))
    return x;
  else
    return " ";
}

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>> return " "
That should be return ' ' (use single quotes for characters).

You need to call that in a loop on each character in your string. Using the transform function from <algorithm> can help you do that in one line of code.

So if I wanted to convert every character that is not a letter, ', or a space to a space, the code would be:

Code:

---

string modifyWord(string ss)
{

    for(int xx = 0; xx < (int)ss.length(); xx++)
    {
        ss[xx] = tolower(ss[xx]);
        if(!isalpha(ss[xx]) && ss[xx] != ' ' && ss[xx] != "'")
            ss[xx] = ' ';
    }

    return ss;
}

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Using the transform function as suggested:

Code:

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#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>

char checkVal(char x)
{
    if(std::isalnum(x))
        return x;
    else
        return ' ';
}

int main()
{
    std::string ss("ab$^&cdefg!@123");

    std::cout << ss << std::endl;

    std::transform(ss.begin(),ss.end(),ss.begin(),checkVal);

    std::cout << ss << std::endl;

    return 0;
}

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Outputs:

Code:

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ab$^&cdefg!@123
ab  cdefg  123

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Why didn't you use checkVal in your loop? Instead you used different code that probably doesn't compile and doesn't do the same thing.

Ok, thanks. When I was trying it a different way however I came across a compiler error that intrigued me. The error was this:

Code:

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18 main.cpp ISO C++ forbids comparison between pointer and integer

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And the code:

Code:

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for(int xx = 0; xx < (int)ss.length(); xx++)
    {
        ss[xx] = tolower(ss[xx]);
        if(!isalpha(ss[xx]) && ss[xx] != "'")
            ss[xx] = ' ';
    }

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Just the statement if(!isalpha(ss[xx])) worked, but when I added && ss[xx] != " ' " (apostrophe), that error arose.

If you need to put the apostrophe character between character marks you need to escape it.

I wouldn't take special measures to prevent a space being replaced with a space.

Code:

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        if(!isalpha(ss[xx]) && ss[xx] != ' ' && ss[xx] != '\'')
            ss[xx] = ' ';

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