Lambda for complex intialization, C++ (clang)

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#include <iostream>
#include <string>
#include <map>

int getDayOfWeekNum2(const std::string& weekDay){
	// Type alias / synonym 
	using WeekDayTable = std::map<std::string, int>;
    static WeekDayTable week_table =
		[](){ // Lambda function
			std::cerr << " [LOG] Initializing month table" << "\n";
			WeekDayTable tbl;
			tbl["Sun"] = 1;
			tbl["Mon"] = 2;
			tbl["Tue"] = 3;
			tbl["Wed"] = 4;
			tbl["Thu"] = 5;
			tbl["Fri"] = 6;
			tbl["Sat"] = 7;
			std::cerr << " [LOG] Month table initialization end. OK." << "\n";
			return tbl;
	   }();
    if(week_table.find(weekDay) != week_table.end())
       return week_table[weekDay];	
    return -1;
}
int main(){
	std::cout << "getDayOfWeekNum2(Mon)   = " << getDayOfWeekNum2("Mon")   << "\n";
	std::cout << "getDayOfWeekNum2(Tue)   = " << getDayOfWeekNum2("Tue")   << "\n";
	std::cout << "getDayOfWeekNum2(Sat)   = " << getDayOfWeekNum2("Sat")   << "\n";
	std::cout << "getDayOfWeekNum2(ERROR) = " << getDayOfWeekNum2("ERROR") << "\n";
	return 0;
};

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Compilation time: 1.34 sec, absolute running time: 0.21 sec, cpu time: 0.13 sec, memory peak: 3 Mb, absolute service time: 1,56 sec