c++ how to replace a string in an array for another string

Question

I am trying a short code that uses an array, I basically want to replace the word hate for love when I call my function WordReplace but I keep printing the same thing:

I don't love c++ I don't love c++

I have tried different things but I am not sure what is wrong

#include <iostream>
#include <string>
using namespace std;

void WordReplace(string*x, int start, int end, string g, string w)
{
   for (int z = start; z <= end; z++)
   {
      if (x[z] == g)
         x[z] == w;

      cout << x[z]<<" ";
   }
}

int main()
{
   string x[4] = {"I", "don't", "hate", "c++"};

   for (int i = 0; i < 4; i++)
   {
      cout << x[i] << " ";
   }
   cout << endl;

   WordReplace(x, 0, 3, "hate", "love");

   cout << endl;

   return 0;
}

`x[z] == w` should be `x[z] = w`. Read about the difference between `=` and `==` in your favorite C++ textbook. — Igor Tandetnik, Sep 07 '17 at 15:02
It might also help to give your variable more intuitive names. At least `g` and `w` don't do it for me. But @IgorTandetnik has your answer. — Frecklefoot, Sep 07 '17 at 15:06
*I have tried different things* -- Except the `std::replace` algorithm function, which does the job in one line of code. The point is that if you're writing code that has the feeling that it has to have been done millions of times before (like replacing x with y), then there is more than likely an STL algorithm function that does the job (if not a set of functions). — PaulMcKenzie, Sep 07 '17 at 15:10
Actually gcc 5.1.0 does not produce any warnings. Reason seems to be that operator is overloaded. When `std::string` replaced with `int` warning "statement has no effect" is produced as expected. — Slava, Sep 07 '17 at 15:26
Try using `std::vector` instead of an array. A lot easier to pass to functions. — Thomas Matthews, Sep 07 '17 at 15:37

Slava · Answer 1 · 2017-09-07T15:24:58.287

5

Just use std::replace:

std::string x[] = {"I", "don't", "hate", "c++"};
std::replace( std::begin( x ), std::end( x ), "hate", "love" );

live example

edited Sep 07 '17 at 15:24

answered Sep 07 '17 at 15:05

Slava

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score 2 · Answer 2 · answered Sep 07 '17 at 15:10

You have c++. Use proper containers (e.g. std::vector).

#include <string>
#include <vector>
#include <iostream>
using namespace std;

void WordReplace(vector<string> &sentence, string search_string,
             string replace_string) {
    for (auto &word : sentence) {
        if (word == search_string)
            word = replace_string;
    }
}

int main() {
    vector<string> sentence{"I", "don't", "hate", "c++"};

    for (const auto word : sentence)
        cout << word << " ";
    cout << endl;

    WordReplace(sentence, "hate", "love");

    for (const auto word : sentence)
        cout << word << " ";
    cout << endl;

     return 0;
}

or even better, don't reinvent the wheel

std::vector<std::string> x {"I", "don't", "hate", "c++"};
std::replace( x.begin(), x.end(), "hate", "love" );

score 1 · Accepted Answer · answered Sep 07 '17 at 15:06

If you want to assign a new value to a variable you need the following syntax:

myVar = myValue;

This will change the value of myVar to myValue.

This construction:

myVar == myValue

is a comparison and is treated as a bool, since it returned true(if myVar equals myValue) and False (if they are not equal). The construction doesn't change the value of myVar or myValue.

In your case you need to replace x[z] == w by x[z] = w, as suggested by Igor

c++ how to replace a string in an array for another string

3 Answers3

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