从Hoogle命令行访问函数的文档

Question

在胡格尔网站上搜索函数时，可以看到与其相关的文档，例如：

mod :: a -> a -> a            infixl 7

    integer modulus, satisfying

    (x `div` y)*y + (x `mod` y) == x

Hoogle还作为命令行可执行文件存在。据我所知，它只显示了函数的签名：

~ ❯❯❯ hoogle --info Prelude.mod
Prelude mod :: Integral a => a -> a -> a

From package base
mod :: Integral a => a -> a -> a

是否有方法通过命令行获取相关文档，就像在线版本中的那样？

Answer 1

使用-i选项。如何获取默认命令(search)的帮助并不明显；下面是如何做到这一点：

$ hoogle search --help
Hoogle v4.2.41, (C) Neil Mitchell 2004-2012
http://haskell.org/hoogle

hoogle [search] [OPTIONS] [QUERY]
  Perform a search

Flags:
  -c --colour --color   Use colored output (requires ANSI terminal)
  -l --link             Give URL's for each result
  -i --info             Give extended information about the first result
  -e --exact            Match names exactly when searching
  -d --databases=DIR    Directories to search for databases
  -s --start=INT        Start displaying results from this point on (1 based)
  -n --count=INT        Maximum number of results to return
  -w --web[=MODE]       Operate as a web tool
  -r --repeat=INT       Run the search multiple times (for benchmarking)
Common flags:
  -? --help             Display help message
  -V --version          Print version information
     --numeric-version  Print just the version number
  -v --verbose          Loud verbosity
  -q --quiet            Quiet verbosity

Answer 2

使用-i标志，Hoogle将显示查询的第一个结果及其哈多克描述：

$ hoogle -i "nub"
nub :: (Eq a) => [a] -> [a]
base Data.List
O(n^2). The nub function removes duplicate elements from
a list. In particular, it keeps only the first occurrence of each
element. (The name nub means `essence'.) It is a special case
of nubBy, which allows the programmer to supply their own
equality test.

如果要查看第一个结果以外的结果的描述，请提供完全限定的名称：

$ hoogle -i "Control.Foldl.nub"
nub :: Ord a => Fold a [a]
foldl Control.Foldl
O(n log n). Fold values into a list with duplicates removed,
while preserving their first occurrences