5. Perl

  • 5.34. Perl formatted output

    Perl is a very powerful text data processing language. Perl can be used in the format to define a template and...
    2025-10-25 13:33:02 UTC
  • 5.35. Perl file operation

    Perl use a variable called the file handle type to manipulate the file. A file handle is required to read or write dat...
    2025-10-25 13:33:05 UTC
  • 5.36. Perl directory operation

    Some standard functions for operating directories are listed below: Opendir DIRHANDLE, EXPR # Open directory Readdir DIRH...
    2025-10-25 13:33:07 UTC
  • 5.37. Perl error handling

    In the process of running the program, you will always encounter all kinds of errors, such as opening a file that does not e...
    2025-10-25 13:33:02 UTC
  • 5.38. Perl special variable

    The Perl language defines some special variables, usually prefixed with $ , @ , or % , such as $_ . Many s...
    2025-10-25 13:33:07 UTC
  • 5.39. Perl regular expression

    Regular expression (regular expression) describes a pattern of string matching, which can be used to check whether a string ...
    2025-10-25 13:33:05 UTC
  • 5.40. Perl sends mail

    If your program runs on Linux/Unix, you can use it in Perl sendmail tool to send mail. The following is a simple scrip...
    2025-10-25 13:33:00 UTC
  • 5.42. Perl object oriented

    There are two different implementations of object-oriented programming in Perl: One is based on the anonymous hash table...
    2025-10-25 13:33:05 UTC
  • 5.43. Perl database connection

    In this section, we will introduce you to the connection to the Perl database. In Perl 5 we can use the DBI module to conn...
    2025-10-25 13:33:04 UTC
  • 5.44. Perl CGI programming

    5.44.1. What is CGI? # CGI is currently maintained by NCSA. NCSA defines CGI as follows: CGI (Common Gateway Interf...
    2025-10-25 13:33:03 UTC
  • 5.45. Perl packages and modules

    Each package in Perl has a separate symbol table, which defines the syntax as follows: package mypack; This statement...
    2025-10-25 13:33:01 UTC
  • 5.46. Perl process management

    You can create processes in different ways in Perl. This tutorial will discuss the management of some processes. You c...
    2025-10-25 13:33:03 UTC
  • 5.47. Perl POD document

    POD (Plain Old Documentation) documents can be embedded in a module or script in Perl. POD is a simple and easy-to-use mar...
    2025-10-25 13:33:02 UTC
《地理信息系统原理、技术与方法》  97

最近几年来,地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持,如城市管理、区划、环境整治等等,地理信息成为信息时代重要的组成部分之一; “数字地球”概念的提出,更进一步推动了作为其技术支撑的GIS的发展。 与此同时,一些学者致力于相关的理论研究,如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面,并且这两个方面构成了相互促进的发展过程。