Is all this Invarient **** er... stuff, premature optimisation?

[Janice Caron]

2008/4/28  <p9e883002 at sneakemail.com>:
>  import std.string;
>
>  int main( string[] args) {
>     char[] a = cast(char[])args[0].toupper();

**** UNDEFINED BEHAVIOR ****
(1) args might be placed in a hardware-locked read-only segment. Then
the following line would fail
(2) there might be other pointers to the string, which expect it never
to change.

>     a[2..5] = "XXX";
>     a = cast(char[])tolower( cast(string)a );
>     writefln(a);
>     return 0;
>  }
>
>  Finally. It works.

But not necessarily on all architectures, because of the undefined
behavior. This is how you do it without undefined behavior.

    import std.string;

    int main( string[] args) {
        string a = args[0].toupper();
        a = a[0..2] ~ "XXX" ~ a[5..$];
        a = a.tolower();
        writefln(a);
        return 0;
    }