Range question

[H. S. Teoh]

I'm trying to write a range-based template that iterates over a range
and returns one of its elements according to some criterion:

        ElementType!R choose(R, E)(R range)
                if (isInputRange!R)
        {
                ElementType!R e;
                while (!range.empty) {
                        if (/* some criterion */) {
                                e = range.front;
                        }
                        range.popFront();
                }
                return e;
        }

But how do I guarantee that e won't be overwritten? For example, if
range.front returns a reference to some buffer that later gets
overwritten by a subsequent operation. Or, if it does get overwritten,
how can I make a copy of its value without depending on specific element
types?

Note that e may be assigned multiple times during the loop, and it's
unknown in advance when the value of e will stop changing, so inserting
a return in the if condition is not possible.


T

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