5. Perl

  • 5.17. Perl switch statement

    One switch statement allows you to test when a variable is equal to multiple values. Each value is called a case, and th...
    2025-10-25 13:33:03 UTC
  • 5.18. Perl cycle

    Sometimes, we may need to execute the same piece of code multiple times. In general, statements are executed sequentially: t...
    2025-10-25 13:33:01 UTC
  • 5.19. Perl while cycle

    while statement when a given condition is true the statement or group of statements is executed repeatedly. The cond...
    2025-10-25 13:33:04 UTC
  • 5.21. Perl for cycle

    Perl for loops are used to execute a sequence of statements multiple times, simplifying the code that manages loop varia...
    2025-10-25 13:33:01 UTC
  • 5.22. Perl foreach cycle

    Perl foreach loop is used to iterate over the value of a list or collection variable. 5.22.1. Grammar # The syn...
    2025-10-25 13:33:06 UTC
  • 5.23. Perl do…while cycle

    Not like for and while loops, they test the loop conditions at theloop header. In Perl the language do...while...
    2025-10-25 13:33:02 UTC
  • 5.24. Perl loop nesting

    Perl language allows the use of another loop within one loop, and here are a few examples to illustrate this concept. ...
    2025-10-25 13:33:00 UTC
  • 5.25. Perl next statement

    Perl next statement is used to stop execution from the next the statement between the beginning of the next statemen...
    2025-10-25 13:33:05 UTC
  • 5.26. Perl last statement

    Perl last statement is used to exit the loop statement block, thus ending the loop last the statement after the stat...
    2025-10-25 13:33:00 UTC
  • 5.27. Perl continue statement

    Perl continue blocks are usually executed before the conditional statement is judged again. continue statement can...
    2025-10-25 13:33:01 UTC
  • 5.28. Perl redo statement

    Perl redo statement directly to the first line of the body of the loop to repeat the execution of the loop redo stat...
    2025-10-25 13:33:02 UTC
  • 5.29. Perl goto statement

    Perl has three forms of goto : got LABLE , goto EXPR , and goto &NAME : Serial number ...
    2025-10-25 13:33:06 UTC
  • 5.30. Perl operator

    An operator is a symbol that tells the compiler to perform specific mathematical or logical operations, such as: 3+2=5 ....
    2025-10-25 13:33:04 UTC
  • 5.31. Perl time date

    In this chapter, we introduce to you Perl treatment of time and date by language. There are several functions for proc...
    2025-10-25 13:33:06 UTC
  • 5.32. Perl subroutine (function)

    Perl subroutines are user-defined functions. Perl subroutine is a separate piece of code that performs a particula...
    2025-10-25 13:33:00 UTC
  • 5.33. Perl reference

    A reference is a pointer. Perl reference is a scalar type that can point to variables, arrays, hash tables (also known a...
    2025-10-25 13:33:02 UTC

Principles, Technologies, and Methods of Geographic Information Systems

 102

In recent years, Geographic Information Systems (GIS) have undergone rapid development in both theoretical and practical dimensions. GIS has been widely applied for modeling and decision-making support across various fields such as urban management, regional planning, and environmental remediation, establishing geographic information as a vital component of the information era. The introduction of the “Digital Earth” concept has further accelerated the advancement of GIS, which serves as its technical foundation. Concurrently, scholars have been dedicated to theoretical research in areas like spatial cognition, spatial data uncertainty, and the formalization of spatial relationships. This reflects the dual nature of GIS as both an applied technology and an academic discipline, with the two aspects forming a mutually reinforcing cycle of progress.