From f26559dcd25b649d37a1a30e087b70b95f530954 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 14 Feb 2025 23:53:46 +0000
Subject: Range adaptor to make triangle strip triples

---
 game/geoData.cpp  | 10 ++++------
 lib/collections.h | 26 ++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/game/geoData.cpp b/game/geoData.cpp
index 552d2ba..cfaf44b 100644
--- a/game/geoData.cpp
+++ b/game/geoData.cpp
@@ -344,12 +344,10 @@ GeoData::setHeights(const std::span<const GlobalPosition3D> triangleStrip, const
 	std::ranges::for_each(newVerts, addVertexForNormalUpdate);
 
 	// Create temporary triangles from triangleStrip
-	std::vector<Triangle<3>> strip;
-	std::transform(
-			strip_begin(triangleStrip), strip_end(triangleStrip), std::back_inserter(strip), [](const auto & newVert) {
-				const auto [a, b, c] = newVert;
-				return Triangle<3> {a, b, c};
-			});
+	const auto strip
+			= materializeRange(triangleStrip | TriangleTriples | std::views::transform([](const auto & newVert) {
+				  return std::make_from_tuple<Triangle<3>>(*newVert);
+			  }));
 	auto getTriangle = [&strip](const auto point) -> const Triangle<3> * {
 		if (const auto t = std::ranges::find_if(strip,
 					[point](const auto & triangle) {
diff --git a/lib/collections.h b/lib/collections.h
index fcd65d3..c81bede 100644
--- a/lib/collections.h
+++ b/lib/collections.h
@@ -197,6 +197,14 @@ template<typename iter> struct stripiter {
 		return *this;
 	}
 
+	constexpr stripiter
+	operator++(int)
+	{
+		auto out {*this};
+		++*this;
+		return out;
+	}
+
 	constexpr stripiter &
 	operator--()
 	{
@@ -205,6 +213,14 @@ template<typename iter> struct stripiter {
 		return *this;
 	}
 
+	constexpr stripiter
+	operator--(int)
+	{
+		auto out {*this};
+		--*this;
+		return out;
+	}
+
 	constexpr auto
 	operator-(const stripiter & other) const
 	{
@@ -235,6 +251,16 @@ strip_end(IterableCollection auto & cont)
 	return stripiter {cont.end()};
 }
 
+struct TriangleTriplesImpl : public std::ranges::range_adaptor_closure<TriangleTriplesImpl> {
+	decltype(auto)
+	operator()(const auto & triangleStrip) const
+	{
+		return std::views::iota(strip_begin(triangleStrip), strip_end(triangleStrip));
+	}
+};
+
+constexpr TriangleTriplesImpl TriangleTriples;
+
 template<typename T, typename Dist, typename Merger>
 void
 mergeClose(std::vector<T> & range, const Dist & dist, const Merger & merger,
-- 
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