Iterate through string char by char

Question

I try to iterate through a string char by char. I tried something like this:

void print(const string& infix)
{
char &exp = infix.c_str();
while(&exp!='\0')
{
         cout<< &exp++ << endl;
    }
}

So this function call print("hello"); should return:

h
e
l
l
o

I try using my code, but it doesn't work at all. btw the parameter is a reference not a pointer. Thank you

The parameter might be a reference, yes, but so is `exp`. By the way, `std::string` has overloaded `operator[]`, and it has `begin()` and `end()` functions, as well as working with the free version of said function pair for iterating. — chris, Feb 03 '13 at 00:52
possible duplicate of [How can I iterate through a string and also know the index (current position)?](http://stackoverflow.com/questions/1315041/how-can-i-iterate-through-a-string-and-also-know-the-index-current-position) — jww, Oct 12 '14 at 04:54
possible duplicate of [For every character in string](http://stackoverflow.com/questions/9438209/for-every-character-in-string) — Csq, Oct 12 '14 at 07:49

score 28 · Answer 1 · answered Feb 03 '13 at 01:19

28

Your code needs a pointer, not a reference, but if using a C++11 compiler, all you need is:

void print(const std::string& infix)
{
    for(auto c : infix)
        std::cout << c << std::endl;
}

answered Feb 03 '13 at 01:19

Mark Tolonen

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1

Best answer. Very clean – Peter Chaula May 12 '20 at 05:53

score 15 · Accepted Answer · answered Feb 03 '13 at 00:53

15

for(unsigned int i = 0; i<infix.length(); i++) {
    char c = infix[i]; //this is your character
}

That's how I've done it. Not sure if that's too "idiomatic".

answered Feb 03 '13 at 00:53

Dhaivat Pandya

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@user1988385, For printing, even `std::cout << infix;` works. – chris Feb 03 '13 at 00:57

David G · Answer 3 · 2013-02-03T01:09:25.837

6

If you're using std::string, there really isn't a reason to do this. You can use iterators:

for (auto i = inflix.begin(); i != inflix.end(); ++i) std::cout << *i << '\n';

As for your original code you should have been using char* instead of char and you didn't need the reference.

edited Feb 03 '13 at 01:09

answered Feb 03 '13 at 00:54

David G

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But, maybe he doesn't only want to copy it? He's simply asked how to iterate through the string character by character. – Dhaivat Pandya Feb 03 '13 at 00:55
Depending on what you're doing with it, there's probably something to replace the `copy` call, though, that works just about the same. – chris Feb 03 '13 at 00:56
The funny thing about the output is that you can and should just `std::cout << infix;`. However, needing to do anything else, an algorithm or iterator loop works. Also, if using `auto` already, I'd use a range-based for loop over an iterator loop as well :p – chris Feb 03 '13 at 01:04

billz · Answer 4 · 2013-02-03T01:03:31.763

0

std::string::c_str() returns const char*, you can't use char& to hold it. Also exp is pointer already, you don't need reference:

Better use iterator though:

void print(const string& infix)
{
  for (auto c = infix.begin(); c!=infix.end(); ++c)
  {
    std::cout << *c << "\n";
  }
  std::cout << std::endl;
}

To fix your original code, try:

void print(const string& infix)
{
  const char *exp = infix.c_str();
  while(*exp!='\0')
  {
    cout << *exp << endl;
    exp++;
   }
 }

edited Feb 03 '13 at 01:03

answered Feb 03 '13 at 00:54

billz

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Is there any reason we would use char* over just a for loop (in my answer)? I've never been sure if that's how other people have done it. – Dhaivat Pandya Feb 03 '13 at 00:56
@DhaivatPandya, Not really, no. Iterating a `std::string` by using a `const char *` seems like a pointless endeavour to me. – chris Feb 03 '13 at 00:57

Iterate through string char by char

4 Answers4