From e81fe345c91a9f70b47b1d30503c0e72870ede5b Mon Sep 17 00:00:00 2001
From: Patrick Wuttke <mewin@mewin.de>
Date: Sun, 25 Jun 2023 19:38:09 +0200
Subject: [PATCH] Added enumerate() function for enumerating an iterator +
 index.

---
 source/mijin/util/iterators.hpp | 91 +++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 source/mijin/util/iterators.hpp

diff --git a/source/mijin/util/iterators.hpp b/source/mijin/util/iterators.hpp
new file mode 100644
index 0000000..b881bab
--- /dev/null
+++ b/source/mijin/util/iterators.hpp
@@ -0,0 +1,91 @@
+#pragma once
+
+#if !defined(MIJIN_UTIL_ITERATORS_HPP_INCLUDED)
+#define MIJIN_UTIL_ITERATORS_HPP_INCLUDED 1
+
+#include <cstddef>
+#include <tuple>
+
+namespace mijin
+{
+template<typename TIdx, typename TIterator>
+struct EnumeratingIterator
+{
+    TIdx idx;
+    TIterator base;
+
+    EnumeratingIterator(TIdx idx_, TIterator base_) noexcept : idx(idx_), base(base_) {}
+    EnumeratingIterator(const EnumeratingIterator&) noexcept = default;
+
+    EnumeratingIterator& operator=(const EnumeratingIterator&) noexcept = default;
+
+    auto operator*() const noexcept
+    {
+        return std::tie(idx, *base);
+    }
+
+    EnumeratingIterator& operator++() noexcept
+    {
+        ++idx;
+        ++base;
+        return *this;
+    }
+
+    EnumeratingIterator operator++(int) noexcept
+    {
+        EnumeratingIterator copy(*this);
+        ++(*this);
+        return copy;
+    }
+
+    EnumeratingIterator& operator--() noexcept
+    {
+        --idx;
+        --base;
+        return *this;
+    }
+
+    EnumeratingIterator operator--(int) noexcept
+    {
+        EnumeratingIterator copy(*this);
+        --(*this);
+        return copy;
+    }
+
+    bool operator==(const EnumeratingIterator& other) const noexcept
+    {
+        return base == other.base; // note: ignoring idx so we don't have to find it out for end()
+    }
+
+    bool operator!=(const EnumeratingIterator& other) const noexcept
+    {
+        return base != other.base; // note: ignoring idx so we don't have to find it out for end()
+    }
+};
+template<typename TIdx, typename TIterator>
+EnumeratingIterator(TIdx, TIterator) -> EnumeratingIterator<TIdx, TIterator>;
+
+template<typename TIdx, typename TIterable>
+struct Enumeratable
+{
+    TIterable& base;
+
+    auto begin() const noexcept
+    {
+        return EnumeratingIterator(TIdx(0), base.begin());
+    }
+
+    auto end() const noexcept
+    {
+        return EnumeratingIterator(TIdx(0), base.end());
+    }
+};
+
+template<typename TIdx = std::size_t, typename TIterable>
+Enumeratable<TIdx, TIterable> enumerate(TIterable& iterable)
+{
+    return {iterable};
+}
+} // namespace mijin
+
+#endif // MIJIN_UTIL_ITERATORS_HPP_INCLUDED
\ No newline at end of file