includes.qmd

---
pagetitle: Includes
---

# Includes {#includes.section}

# Stan 文件的包含

本节译者：李泓玮

Stan allows one file to be included within another file using a syntax
similar to that from C++.  For example, suppose the file
`my-std-normal.stan` defines the standard normal log probability
density function (up to an additive constant).

Stan 允许一个文件包含在另一个文件中，使用的语法与 C++ 类似。例如，假设文件 `my-std-normal.stan` 定义了标准正态对数概率密度函数（忽略常数项）。

``` stan
functions {
  real my_std_normal_lpdf(vector y) {
    return -0.5 * y' * y;
  }
}
```

Suppose we also have a file containing a Stan program with an include statement.

假设我们还有一个文件，凭借 include 语句包含 Stan 程序。

``` stan
#include my-std-normal.stan
parameters {
  real y;
}
model {
  y ~ my_std_normal();
}
```

This Stan program behaves as if the contents of the file
`my-std-normal.stan` replace the line with the `#include`
statement, behaving as if a single Stan program were provided.

在这个 Stan 程序中，`#include` 语句这一行可以替换为文件 `my-std-normal.stan` 的内容，也就是说这一行相当于一个单独的 Stan 程序。

``` stan
functions {
  real my_std_normal_lpdf(vector y) {
    return -0.5 * y' * y;
  }
}
parameters {
  real y;
}
model {
  y ~ my_std_normal();
}
```

There are no restrictions on where include statements may be placed
within a file or what the contents are of the replaced file.

对于 include 语句在文件中的位置以及具体包含什么文件，没有限制。

### Space before includes {-}

### include 语句前的空格 {-}

It is possible to use includes on a line non-initially.  For example,
the previous example could've included space before the `#` in the
include line:

include 语句所在行，可以不顶格书写。例如，在前面的例子中， `#` 前面可以有空格：

``` stan
    #include my-std-normal.stan
parameters {
// ...
```

If there is initial space before an include, it will be discarded.

如果 include 前存在空格，这些空格将被忽略。

### Comments after includes {-}

### include 语句后的注释 {-}

It is also possible to include line-based comments after the include.
For example, the previous example can be coded as:

也可以在 include 之后添加对该行的注释。例如，前面的例子可以写成：

``` stan
#include my-std-normal.stan  // definition of standard normal
parameters {
// ...
```

Line comments are discarded when the entire line is replaced with the
contents of the included file.

如果 include 这一行都替换为相关文件的内容，就不再需要行注释。

## Recursive includes

## 递归的 include

Recursive includes will be ignored. For example, suppose
`a.stan` contains

递归的 include 将导致编译器错误。例如，假设 `a.stan` 中有

``` stan
#include b.stan
```

and `b.stan` contains

而 `b.stan` 中有

``` stan
#include a.stan
```

This will result in an error explaining the circular dependency:

这将导致一个解释循环依赖的报错：

``` stan
Syntax error in './b.stan', line 1, column 0, included from
'./a.stan', line 1, column 0, included from
'./b.stan', line 1, column 0, included from
'a.stan', line 1, column 0, include error:
   -------------------------------------------------
     1:  #include a.stan
         ^
   -------------------------------------------------

File a.stan recursively included itself.
```

## Include paths

## include 的路径

The Stan interfaces may provide a mechanism for specifying a sequence of system paths in which to search for include files. The file included is the first one that is found in the sequence.

Stan 接口可以提供一种机制，用于指定搜索包含文件的系统路径序列。包含的文件是在序列中找到的第一个文件。

### Slashes in include paths {-}

### include 路径中的斜杠 {-}

If there is not a final `/` or `\` in the path, a `/` will be
appended between the path and the included file name.

如果路径末尾没有 `/` 或 `\` ，则路径与包含的文件名之间将追加一个 `/` 。