PSRangeCounter

Counting range-for loop in C++

#include "range_counter.h"

If you have the ability to use C++20, you can use std::ranges::views::iota(0,N) for the similar capabilities.

Use cases:

• counting with a range-for loop (MISRA-C++ compliance)
• input subsequent integral values starting with 0 for an algorithm call

The types for iterators and zero-based ranges are enum types to ensure efficient pass by value, regardless of bad ABI for class types.

Example usage:

#include "range_counter.h"
using namespace ps_counter::literals;
// or using ps_counter::operator""_times;


void testRangeLoopLoops(){
	size_t sum{};
	for(auto const i : 11_times){ // or 11_up_to
		sum +=i;
	}
	ASSERT_EQUAL(55u,sum); // [0..10]
}
void test_with_algorithm(){
	std::string s{};
	using it=ps_counter::iterator;
	std::transform(it{},it{10},std::back_inserter(s),[](size_t i){return std::to_string(i)[0];});
	ASSERT_EQUAL("0123456789",s);
}

play with it on godbolt: https://godbolt.org/z/n9137oh67

Using my reverse range adapter, one can even walk backwards:

#include "reversed.h"

#include <algorithm>
#include <iterator>

#include <string>

using adapter::reversed;

void testReversedRange(){
	std::string sum{};
	for(auto const i : reversed(11_times) ){
		sum.append(std::to_string(i));
	}
	ASSERT_EQUAL("109876543210",sum);
}

Or simpler, use ps_counter::reverse_range by using suffix _down_from

void testForwardReversedRange(){
	std::string sum{};
	for(auto const i : 11_down_from ){
		sum.append(std::to_string(i));
	}
	ASSERT_EQUAL("109876543210",sum);
}

Ranges with non-zero start (only positive integers!)

#include "range_counter_range.h"

As an exercise of integer parsing with template UDL operators, I implemented also ranges where you can specify start and end. However, this requires a class type for keeping both values around, instead of a simple enum.

Also the syntax for specifying the ranges is a bit unintuitive, because it employs valid floating point syntax to separate start from end and to allow inclusive and exclusive ranges to be specified with the same UDL suffix _range. The underlying scaffolding needed in addtion to the contents of "range_counter.h" is not part of the public API. If you need to specify a range with variable content, use a ps_counter::(reverse_)iterator pair or in case of C++20 std::ranges::iota_view or its companion std::views::iota.

The following are supported . - dot = half-open range, ' - quote = closed range, counting down is automatically determined if the first integer is bigger than the second one:

• 10_range -> 0,1,2,3,4,5,6,7,8,9
• .10_range -> 0,1,2,3,4,5,6,7,8,9,10
• 5.10_range -> 5,6,7,8,9,10
• 1'10_range -> 1,2,3,4,5,6,7,8,9
• 5.1_range -> 5,4,3,2,1
• 5'1_range -> 4,3,2,1
• 5'0_range -> 4,3,2,1,0