A question about "std::string::substr"

In all the references I saw, the arguments to the string::substr function is in index numbers.
Can it be generalized to string::iterator"s?
or..Is the iterator value same as the position...
or How do I generate the ^later from the ^former...?

substr does not take iterators. string has a constructor that takes iterators, plus you have all the stuff in <algorithm>, like copy.

(EDIT: Looks like I read it backwards. If you have indices and want iterators (for reasons unknown), then ignore this and read whiteflags.)

A pointer is an iterator type, so &string[pos] is an expression that will get you an iterator, but not necessarily a std::string::iterator. For that instead, write:

Code:

---

string.begin() + pos

---

Sorry..I didn't fully get that..
@whiteflags : I think I need the reverse of that... I have the iterator ...but not the position number...

Or ..would getting rid of the iterators and using the position as a control for the master loop be a better idea ?

Quote:

---

Originally Posted by manasij7479

I think I need the reverse of that... I have the iterator ...but not the position number...

---

You can subtract the return value of begin(), or more generally use std::distance().

Does iterator - xx.begin() give the position or is there a +1 necessary..?
And When I have the two positions a and b... is (b-a) the distance or is it (b-a +1) ?

Code:

---

begin() -> s[0] = 'h';
 s[1] = 'e';
 s[2] = 'l';
 s[3] = 'l';
 s[4] = 'o';
 s[5] = ?? <- end()

---

std::distance() makes this irrelevant, but index number 4 is the 5th character, because indexes start from 0. If you want to use an index, a - b is correct math. The other number, a-b+1, has no technical value, it's just how you look at it.

Also to keep in mind: usual custom, especially with iterators, is for the second iterator to not be included in the range (e.g., begin() points in the string, end() points one-past-the-end). So depending on how you set that up also plays a factor in how many items you need.

...Well.... this illustrates the problem I'm facing...