Hiding the Iterator
Other languages let you write for loops that hide the iterator. C++ can do that, too.
Instead of writing
double total = 0.0;
for (auto p = values.begin(); p != values.end(); ++p) {
total += *p;
}
we can instead say
double total = 0.0;
for (double v : values) {
total += v;
}
Okay, I didn't like this iterator stuff much until now. But I like not having any
*things anywhere!
Well… if we wanted to write to the value to change values in our data structure, we should really make the
doubleadouble&so we have a reference to the original value in the data structure.-
…
How It Works
When we write
for (TYPE var : thing) {
... var ...
}
C++ basically turns it into
{
auto _past_end = std::end(thing);
for (auto _i = std::begin(thing); _i != _past_end; ++_i) {
TYPE var = *i;
... var ...
}
}
(std::begin and std::end call begin() and end() member functions on classes, but also “do the right thing” for primitive arrays.)
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