This Go code defines and demonstrates the creation and usage...

This Go code defines and demonstrates the creation and usage of a map with keys of type string and values of a custom Vertex struct. Here's what the code does, step by step:

1. Package and imports:

   • The program starts with the package main declaration, indicating it is an executable program.
   • The program imports the fmt package to allow formatted I/O operations, such as printing.

2. Define the Vertex struct:

   • A struct named Vertex is defined, which has two fields: Lat (latitude) and Long (longitude), both of type float64.

3. Declare a map variable m:

   • A global variable m of type map[string]Vertex is declared. This map will use string keys and Vertex struct values.

4. Function main:

   • The main function is the entry point of the Go program.
   • Inside main, the map m is initialized with make(map[string]Vertex), creating an empty map.
   • A key-value pair is added to the map: the key is "Bell Labs", and the value is a Vertex struct with Lat = 40.68433 and Long = -74.39967.
   • The value associated with the key "Bell Labs" in the map is retrieved and printed using fmt.Println.

5. Output:

   • The program outputs the value of m["Bell Labs"], which is the Vertex struct added earlier. The output will be:

   {40.68433 -74.39967}
   

Summary: This code defines a map that associates string keys with coordinates (latitude and longitude), stores a Vertex for the key "Bell Labs", and prints it.