Julia 环境中的继承

Question

我不清楚在 Julia 中使用 Pkg.generate() 创建的环境是否完全隔离，或者它们是否继承了分层目录树中目录中安装的一些模块/包。如果是这种情况，有什么办法可以从一个完全空的环境开始？我认为 Base 环境是强制性的，对吧？谢谢。

Answer 1

Julia 中的环境是堆叠的——有一个默认环境（以 Julia 版本命名，例如 @1.8 代表 Julia 1.8.x），默认情况下可以从任何活动环境访问。文档的相关部分可以在here 找到。

从那里引用：

第三种也是最后一种环境是通过叠加多个环境来组合其他环境，使每个环境中的包在单个复合环境中可用。这些复合环境称​​为环境堆栈。 Julia LOAD_PATH 全局定义了一个环境堆栈——Julia 进程运行的环境。如果您希望您的 Julia 进程只能访问一个项目或包目录中的包，请将其设为 LOAD_PATH 中的唯一条目。

要查看实际效果：

julia> Base.LOAD_PATH
3-element Vector{String}:
 "@"
 "@v#.#"
 "@stdlib"

这里 @v#.# 是默认环境，@stdlib 顾名思义是标准库（例如 [at least for now!] DelimitedFiles、Statistics）。 LOAD_PATH 的帮助条目提供了一些更详细的信息：

help?> LOAD_PATH
search: LOAD_PATH

  LOAD_PATH

  An array of paths for using and import statements to consider as project environments or package directories when loading code. It is populated based on the JULIA_LOAD_PATH environment variable if set;
  otherwise it defaults to ["@", "@v#.#", "@stdlib"]. Entries starting with @ have special meanings:

    •  @ refers to the "current active environment", the initial value of which is initially determined by the JULIA_PROJECT environment variable or the --project command-line option.

    •  @stdlib expands to the absolute path of the current Julia installation's standard library directory.

    •  @name refers to a named environment, which are stored in depots (see JULIA_DEPOT_PATH) under the environments subdirectory. The user's named environments are stored in ~/.julia/environments so
       @name would refer to the environment in ~/.julia/environments/name if it exists and contains a Project.toml file. If name contains # characters, then they are replaced with the major, minor and
       patch components of the Julia version number. For example, if you are running Julia 1.2 then @v#.# expands to @v1.2 and will look for an environment by that name, typically at
       ~/.julia/environments/v1.2.

  The fully expanded value of LOAD_PATH that is searched for projects and packages can be seen by calling the Base.load_path() function.

如果需要，您可以从 LOAD_PATH 中删除所有内容：

C:>set JULIA_LOAD_PATH=""

C:>julia -q


julia> Base.LOAD_PATH
1-element Vector{String}:
 """"