Added examples of std::format

Examples/src/Streams/format/Makefile

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+############################################################
+#
+# An example of Makefile for the course on 
+# Advanced Programming for Scientific Computing
+# It should be modified for adapting it to the various examples
+#
+############################################################
+#
+# The environmental variable PACS_ROOT should be set to the
+# root directory where the examples reside. In practice, the directory
+# where this file is found. The resolution of PACS_ROOT is made in the
+# Makefile.h file, where other important variables are also set.
+# The only user defined variable that must be set in this file is
+# the one indicating where Makefile.h resides
+
+MAKEFILEH_DIR=../../../
+#
+include $(MAKEFILEH_DIR)/Makefile.inc
+#
+# You may have an include file also in the current directory
+#
+-include Makefile.inc
+
+#
+# The general setting is as follows:
+# mains are identified bt main_XX.cpp
+# all other files are XX.cpp
+#
+
+# get all files *.cpp
+SRCS=$(wildcard *.cpp)
+# get the corresponding object file
+OBJS = $(SRCS:.cpp=.o)
+# get all headers in the working directory
+HEADERS=$(wildcard *.hpp)
+#
+exe_sources=$(filter main%.cpp,$(SRCS))
+EXEC=$(exe_sources:.cpp=)
+
+#========================== ORA LA DEFINIZIONE DEGLI OBIETTIVI
+.phony= all clean distclean doc
+
+.DEFAULT_GOAL = all
+
+all: $(DEPEND) $(EXEC)
+
+clean:
+	$(RM) -f $(EXEC) $(OBJS)
+
+distclean:
+	$(MAKE) clean
+	$(RM) -f ./doc $(DEPEND)
+	$(RM) *.out *.bak *~
+
+doc:
+	doxygen $(DOXYFILE)
+
+$(EXEC): $(OBJS)
+
+$(OBJS): $(SRCS)
+
+$(DEPEND): $(SRCS)
+	$(RM) $(DEPEND)
+	for f in $(SRCS); do \
+	$(CXX) $(STDFLAGS) $(CPPFLAGS) -MM $$f >> $(DEPEND); \
+	done
+
+-include $(DEPEND)
+
+
+
+

Examples/src/Streams/format/README.md

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+# The std::format utility
+The `std::format` utility is a new feature in C++20 that allows you to format strings in a more readable and maintainable way. It is similar to `printf` but with a more modern syntax.
+
+The `std::format` function is defined in the `<format>` header file. It takes a format string and a list of arguments, and returns a formatted string.
+
+## Basic usage
+Here is a simple example of using `std::format`:
+
+```cpp
+#include <format>
+#include <iostream>
+  std::string message = std::format("Hello, {}!", "world");
+  std::cout << message << std::endl;
+```
+In the given file you find more significant examples of the `std::format` utility. This utility makes writing formatted output much easier and more readable. Moreover, comparing to C-style formatting, it is type-safe and more secure.
+
+# What do I learn here?
+You will learn how to use the `std::format` utility to format strings in C++20. More details may be found in the [C++ reference](https://en.cppreference.com/w/cpp/utility/format/format).

Examples/src/Streams/format/main_format.cpp

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+#include <format>
+#include <iostream>
+#include <numbers>
+int
+main()
+{
+  std::string name = "John";
+  int         age = 30;
+  double      height = 1.75;
+
+  auto formattedString =
+    std::format("Name: {}, Age: {}, Height: {:.2f}", name, age, height);
+  std::cout << formattedString << std::endl;
+  formattedString =
+    std::format("Centered: {:^}, LeftJustified: {:<d}, RightJustified: {:>.2f}",
+                name, age, height);
+  std::cout << formattedString << std::endl;
+  formattedString =
+    std::format("With a space of 8 and - as filling\nCentered: {:-^8}, "
+                "LeftJustified: {:-<8d}, RightJustified: {:->8.2f}",
+                name, age, height);
+  std::cout << formattedString << std::endl;
+  std::cout << std::format("42 in binary format: {:b}", 42) << std::endl;
+  std::cout << std::format("42 in hex format: {:x}", 42) << std::endl;
+  std::cout << std::format("Maybe you need to print {{}} before printing {:d}",
+                           42)
+            << std::endl;
+  // different precisiones
+  std::cout << std::format("Pi with 2 decimal places: {:.2f}", std::numbers::pi)
+            << std::endl;
+  std::cout << std::format("Pi with 4 decimal places: {:.4f}", std::numbers::pi)
+            << std::endl;
+  std::cout << std::format("Pi with 15 decimal places: {:.15f}",
+                           std::numbers::pi)
+            << std::endl;
+  return 0;
+}