5. Perl

  • 5.1. Perl tutorial

    Perl is the abbreviation of Practical Extraction and Report Language and can be translated into “practical report extract...
    2025-10-25 13:33:03 UTC
  • 5.2. Perl introduction

    Perl, a feature-rich computer programming language, runs on more than 100 computer platforms and is suitable for a wide rang...
    2025-10-25 13:33:03 UTC
  • 5.3. Perl environment installation

    Before we can start learning the Perl language, we need to install the Perl execution environment. Perl can run on the fol...
    2025-10-25 13:33:02 UTC
  • 5.4. Perl basic syntax

    Perl borrows the features of C, sed, awk, shell scripts, and many other programming languages, and the syntax is somewhat si...
    2025-10-25 13:33:01 UTC
  • 5.5. Perl data type

    Perl is a weakly typed language, so variables do not need to specify a type,and the Perl interpreter automatically selects t...
    2025-10-25 13:33:06 UTC
  • 5.6. Perl variable

    A variable is data stored in memory, and creating a variable opens up a space in memory. The interpreter determines the st...
    2025-10-25 13:33:06 UTC
  • 5.7. Perl scalar

    Scalar is a simple data unit. Scalars can be an integer, floating point, character, string, paragraph, or a complete web p...
    2025-10-25 13:33:07 UTC
  • 5.8. Perl array

    Perl array is a list variable that stores scalar values, and variables can be of different types. Array variables to ...
    2025-10-25 13:33:06 UTC
  • 5.9. Perl hash

    The hash is key/value that’s right Gather. Perl hash variable in the starts with the percent sign (%). Access th...
    2025-10-25 13:33:01 UTC
  • 5.10. Perl conditional statement

    Perl conditional statement is the result of the execution of one or more statements True or False to determine t...
    2025-10-25 13:33:04 UTC
  • 5.11. Perl IF statement

    Perl if statement consists of a Boolean expression followed by one or more statements. 5.11.1. Grammar # The sy...
    2025-10-25 13:33:04 UTC
  • 5.12. Perl IF…ELSE statement

    One if statement can be followed by an optional else statement else statement in a Boolean expression false ...
    2025-10-25 13:33:01 UTC
  • 5.13. Perl IF…ELSIF statement

    One if statement can be followed by an optional elsif statement, and then follow another else statement. This ...
    2025-10-25 13:33:04 UTC
  • 5.14. Perl UNLESS statement

    One unless statement consists of a Boolean expression followed by oneor more statements. 5.14.1. Grammar # The ...
    2025-10-25 13:33:06 UTC
  • 5.15. Perl UNLESS…ELSE statement

    One unless statement can be followed by an optional else statement else statement in a Boolean expression true...
    2025-10-25 13:33:00 UTC
  • 5.16. Perl UNLESS…ELSIF statement

    One unless statement can be followed by an optional elsif statement, and then follow another else statement. T...
    2025-10-25 13:33:04 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。