Modify char in string

[bearophile via Digitalmars-d-learn]

Tim:

> is there any chance to modify a char in a string like:
>
> void main()
> {
>    string sMyText = "Replace the last char_";
>    sMyText[$ - 1] = '.';
> }
>
> But when I execute the code above I'm always getting "cannot 
> modify immutable expression at sMyText[__dollar -1LU]". I 
> though D supported such modifications anytime. How can I do 
> that now...?

D strings are immutable. And mutating immutable variables is a 
bug in D. So you can't do that. You have to work around the 
problem. One solution is to not have a string, but something more 
like a char[] in the first place, and mutate it.

If you have a string, you can do (this works with the current GIT 
DMD compiler):



/// Not Unicode-safe.
string dotLast(in string s) pure nothrow {
     auto ds = s.dup;
     ds[$ - 1] = '.';
     return ds;
}

void main() {
     import std.stdio;

     immutable input = "Replace the last char_";
     immutable result = input.dotLast;
     result.writeln;
}


That code doesn't work if your text contains more than the Ascii 
chars.

Bye,
bearophile