[ruby-core:103049] [Ruby master Misc#17751] Do these instructions (<<, +, [0..n]) modify the original string without creating copies?

Issue #17751 has been updated by mame (Yusuke Endoh).


> I would like to do something similar to (<<), which I understand does not create copies.

There is `String#prepend` method.

```
str.prepend(header)
```

> I also have this other code and I don't know if it is an "in place" modifier:

`str[0..2] = ""` is an in-place operation.

Note, however, that these operations (`String#prepend` and `[]=`) may take a long time.
They do not create another huge string, but they copy the whole content in place, which may take O(n).
If you are worried about only memory consumption, they may work.
But if you want to make your code memory-efficient and fast, they will not solve your issue.

> In short, I want to know what instructions I should use to remove a given range from a string and how to concatenate to both the beginning and end of the target string without having to create copies.

In general, it is difficult to do all operations efficiently. If you explain your real problem, we may propose a good solution.

----------------------------------------
Misc #17751: Do these instructions (<<,+,[0..n]) modify the original string without creating copies?
https://bugs.ruby-lang.org/issues/17751#change-91110

* Author: stiuna (Juan Gregorio)
* Status: Open
* Priority: Normal
----------------------------------------
In my program a string increases considerably in size inside a loop, at the end of that loop a header is created that will have to go to the beginning of that string.

During the whole loop:

``` ruby
str << "some data"
```


At the end:

``` ruby
header = "other data"
str = header + str
```

I understand that using (+) creates a copy to then modify the original variable, that is not desirable, I would like to do something similar to (<<), which I understand does not create copies.

If I do this:
``` ruby
header << str
```

I would have two variables with a very large size.

I also have this other code and I don't know if it is an "in place" modifier:
``` ruby
str = "12345"
str[0..2] = ""
#s => 45
```


In short, I want to know what instructions I should use to remove a given range from a string and how to concatenate to both the beginning and end of the target string without having to create copies.



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