cleanup: implement index_of() and index_of_if() generics

Search the index of an item in a container. Compare by
equality or a lambda. The lack of these have annoyed me for a
long time. Return the index of the first found element or
-1 if no element found.

Currently, only supports random-access operators. Might be
trivially changed for forward iterators.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/range.h

@@ -82,4 +82,20 @@ public:
 	}
 };
 
+// Find the index of an element in a range. Return -1 if not found
+// Range must have a random access iterator.
+template <typename Range, typename Element>
+int index_of(const Range &range, const Element &e)
+{
+	auto it = std::find(std::begin(range), std::end(range), e);
+	return it == std::end(range) ? -1 : it - std::begin(range);
+}
+
+template <typename Range, typename Func>
+int index_of_if(const Range &range, Func f)
+{
+	auto it = std::find_if(std::begin(range), std::end(range), f);
+	return it == std::end(range) ? -1 : it - std::begin(range);
+}
+
 #endif

qt-models/divepicturemodel.cpp

@@ -242,10 +242,8 @@ int DivePictureModel::rowCount(const QModelIndex&) const
 
 int DivePictureModel::findPictureId(const std::string &filename)
 {
-	for (int i = 0; i < (int)pictures.size(); ++i)
+	return index_of_if(pictures, [&filename](const PictureEntry &p)
-		if (pictures[i].filename == filename)
+				     { return p.filename == filename; });
-			return i;
-	return -1;
 }
 
 static void addDurationToThumbnail(QImage &img, duration_t duration)

qt-models/divetripmodel.cpp

@@ -1008,29 +1008,19 @@ void DiveTripModelTree::addDivesToTrip(int trip, const QVector<dive *> &dives)
 
 int DiveTripModelTree::findTripIdx(const dive_trip *trip) const
 {
-	for (auto [i, item]: enumerated_range(items)) {
+	return index_of_if(items, [trip] (const Item &item)
-		if (item.d_or_t.trip == trip)
+				  { return item.d_or_t.trip == trip; });
-			return i;
-	}
-	return -1;
 }
 
 int DiveTripModelTree::findDiveIdx(const dive *d) const
 {
-	for (auto [i, item]: enumerated_range(items)) {
+	return index_of_if(items, [d] (const Item &item)
-		if (item.isDive(d))
+				  { return item.isDive(d); });
-			return i;
-	}
-	return -1;
 }
 
 int DiveTripModelTree::findDiveInTrip(int tripIdx, const dive *d) const
 {
-	const Item &item = items[tripIdx];
+	return index_of(items[tripIdx].dives, d);
-	for (auto [i, dive]: enumerated_range(item.dives))
-		if (dive == d)
-			return i;
-	return -1;
 }
 
 int DiveTripModelTree::findInsertionIndex(const dive_trip *trip) const