Re: Variables in for loop (style issue)

"Victor Bazarov" <>
11 May 2006 19:43:08 -0400
Vidar Hasfjord wrote:

Carl Barron wrote:

if the variables are of the same type then something like
  `for(int i(0),max(10);i!=max;++i) { /* */}
is legal and intializes two ints in the for loop without adding
complexity of member function calls.

The original poster included and expressed displeasure about this very
option. He wants a construct that clearly expresses that the end value
(max) is a constant. I was responding to that, and for that the only
solution is an aggregate, unless you accept declarations outside the
initializer of the for-loop.

Personally, I don't use "index". I use any and all of the idioms
presented by the original poster without dwelling to much on it.
Instead I look forward to C++0x with "foreach" --- as well as concepts
(which will allow containers as arguments to algorithms, i.e. no more
of the "begin" and "end" clutter when you want to process the whole
container) and lamdas (for use with for_each and other concise
iterative constructs). I imagine the ideal loop for iterating the
indexes of a container would be:

foreach (size_t i : index_range (v)) //...

template<class T> class iterate {
    T i;
    const T max;
    iterate(T i, T max) : i(i), max(i) {}
    bool not_yet() const { return i < max; }
    void operator++() { ++i; }
    T var() const { return i; }
    T invar() const { return max; }
// or even
    operator T() const { return i; }
    for (iterate<int> v(0,10); v.not_yet(); ++v) {
       ... v.var() ...
// or even
       ... [v] ...


[Disclaimer: code untested]

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