Simplify with std::map::insert

src/Buffer.cpp

@@ -3773,9 +3773,7 @@ void Buffer::Impl::updateMacros(DocIterator & it, DocIterator & scope)
 
 				// register its position, but only when it is
 				// included first in the buffer
-				if (children_positions.find(child) ==
-					children_positions.end())
-						children_positions[child] = it;
+				children_positions.insert({child, it});
 
 				// register child with its scope
 				position_to_children[it] = Impl::ScopeBuffer(scope, child);

src/frontends/qt/GuiSymbols.cpp

@@ -473,11 +473,8 @@ void GuiSymbols::updateSymbolList(bool update_combo)
 		++numItem;
 		if (show_all || (c >= range_start && c <= range_end))
 			s.append(c);
-		if (update_combo) {
-			QString block = getBlock(c);
-			if (used_blocks.find(block) == used_blocks.end())
-				used_blocks[block] = numItem;
-		}
+		if (update_combo)
+			used_blocks.insert({getBlock(c), numItem});
 	}
 	model_->setSymbols(s, enc);
 

src/output_latex.cpp

@@ -600,8 +600,7 @@ void addArgInsets(Paragraph const & par, string const & prefix,
 		string const name = prefix.empty() ?
 			arg->name() : split(arg->name(), ':');
 		size_t const nr = convert<size_t>(name);
-		if (ilist.find(nr) == ilist.end())
-			ilist[nr] = arg;
+        ilist.insert({nr, arg});
 		Layout::LaTeXArgMap::const_iterator const lit =
 			latexargs.find(arg->name());
 		if (lit != latexargs.end()) {

src/tex2lyx/Preamble.cpp

@@ -445,8 +445,7 @@ int Preamble::getSpecialTableColumnArguments(char c) const
 void Preamble::add_package(string const & name, vector<string> & options)
 {
 	// every package inherits the global options
-	if (used_packages.find(name) == used_packages.end())
-		used_packages[name] = split_options(h_options);
+    used_packages.insert({name, split_options(h_options)});
 
 	// Insert options passed via PassOptionsToPackage
 	for (auto const & p : extra_package_options_) {